Proof of work does not make attacks by hackers impossible, but it does make them somewhat useless. If a hacker wanted to coordinate an attack on the blockchain, they would need to solve complex computational math problems at 1 in 5.8 trillion odds just like everyone else. The cost of organizing such an attack would almost certainly outweigh the benefits.
The common assumption that Bitcoins are stored in a wallet is technically incorrect. Bitcoins are not stored anywhere. Bitcoin balances are kept using public and private “keys,” which are long strings of numbers and letters linked through the mathematical encryption algorithm that was used to create them. The public key (comparable to an international bank account number or IBAN) serves as the address published to the world, and to which others may send Bitcoins.
Bitcoin is a peer-to-peer payment network established in 2009 that uses a virtual currency, the bitcoin, to conduct transactions. Unlike currencies issued by nations, Bitcoin is independent of any country or stock exchange and is entirely digital, with no ties to a central bank, company, or organization.[1][2] It is used as an investment and medium of exchange by all members of its network. Getting bitcoins of your own is thus a matter of becoming a part of the Bitcoin network by setting up a bitcoin account and wallet.
Transparency: even though personal information on blockchain is kept private, the technology itself is almost always open source. That means that users on the blockchain network can modify the code as they see fit, so long as they have a majority of the network’s computational power backing them. Keeping data on the blockchain open source also makes tampering with data that much more difficult. With millions of computers on the blockchain network at any given time, for example, it is unlikely that anyone could make a change without being noticed.
Venture capitalists, such as Peter Thiel's Founders Fund, which invested US$3 million in BitPay, do not purchase bitcoins themselves, but instead fund bitcoin infrastructure that provides payment systems to merchants, exchanges, wallet services, etc.[148] In 2012, an incubator for bitcoin-focused start-ups was founded by Adam Draper, with financing help from his father, venture capitalist Tim Draper, one of the largest bitcoin holders after winning an auction of 30,000 bitcoins,[149] at the time called "mystery buyer".[150] The company's goal is to fund 100 bitcoin businesses within 2–3 years with $10,000 to $20,000 for a 6% stake.[149] Investors also invest in bitcoin mining.[151] According to a 2015 study by Paolo Tasca, bitcoin startups raised almost $1 billion in three years (Q1 2012 – Q1 2015).[152]
Proof of work does not make attacks by hackers impossible, but it does make them somewhat useless. If a hacker wanted to coordinate an attack on the blockchain, they would need to solve complex computational math problems at 1 in 5.8 trillion odds just like everyone else. The cost of organizing such an attack would almost certainly outweigh the benefits.
Say John buys a lemonade from Sandy’s lemonade stand. On John’s copy of the blockchain, he marks that transaction down: “John bought Lemonade from Sandy, $2.” His copy gets spread around town to all the lemonade stands and lemonade buyers, who add this transaction to their own copies. By the time John has finished drinking that lemonade, everyone’s blockchain ledger shows that he bought his lemonade from Sandy for $2.

In Person: Over-the-counter platforms such as CoinCola or LocalBitcoins are resources to find people in your area to trade bitcoins with. Trust and security can be a concern, which is why it's recommended you transact in a public place, and not necessarily with large amounts of cash. Some of those platforms, such as CoinCola, will allow its users to upload an ID proof. In this case, you will be able require the ID proof of your trade partner for added security.

A small class of digital currencies known as privacy coins aims to make blockchain-based transactions untraceable. They do this by beefing up the protocols designed to obscure the identity of the sender and receiver of funds, as well as the dollar amount being sent. Yes, privacy coins have been accused of being a haven for the criminal community. However, most privacy coin and blockchain developers also suggest that this is a minute component of their community, and that nearly all members are legitimate consumers and businesses.
In the financial world the applications are more obvious and the revolutionary changes more imminent. Blockchains will change the way stock exchanges work, loans are bundled, and insurances contracted. They will eliminate bank accounts and practically all services offered by banks. Almost every financial institution will go bankrupt or be forced to change fundamentally, once the advantages of a safe ledger without transaction fees is widely understood and implemented. After all, the financial system is built on taking a small cut of your money for the privilege of facilitating a transaction. Bankers will become mere advisers, not gatekeepers of money. Stockbrokers will no longer be able to earn commissions and the buy/sell spread will disappear.
The use of bitcoin by criminals has attracted the attention of financial regulators, legislative bodies, law enforcement, and the media.[217] In the United States, the FBI prepared an intelligence assessment,[218] the SEC issued a pointed warning about investment schemes using virtual currencies,[217] and the U.S. Senate held a hearing on virtual currencies in November 2013.[219] The U.S. government claimed that bitcoin was used to facilitate payments related to Russian interference in the 2016 United States elections.[220]
To sum it up, Bitcoin lending is a good way to make more Bitcoins from what you already have. And please notice this disclaimer: only lend through sites that you trust. Such sites will comply with the usual requirements that you expect from non-Bitcoin related sites as well. That means they have proper terms and conditions in place, they disclose their status of incorporation and contact details. Some sites in the Bitcoin world do not do this and in the end people wonder what happened to their Bitcoins. Therefore, when you earn Bitcoins from Bitcoin lending watch who you deal with and only use Bitcoins which you can afford to lose.
Bitcoin’s first mover advantage, popularity, and network effect have cemented it as the most popular cryptocurrency with the largest market cap. Rivals like Litecoin may have numerous technical advantages over Bitcoin’s algorithm (see more about that here), but they only hold a fraction of Bitcoin’s market cap and their dwindling communities largely consist of loyalists, speculators, and antagonistic anti-Bitcoin buyers.
Bitcoin’s popularity has undeniably been its number one advantage over the numerous other cryptocurrencies. By gaining a large number of adopters and users, Bitcoin has achieved a network effect that attracts even more users. Users who would otherwise be more apprehensive investing in a relatively unknown and unproven digital currency are reassured by Bitcoin’s performance over time, its growing community, and the fact that people they know are adopting cryptos.
The average price of a bitcoin can increase and decrease unpredictably. For example, in one week in November, 2015 Bitcoin went from $318 on a Monday to $492 on a Wednesday, falling back under $400 by Thursday.[14] Do not put too much money into bitcoin, as it's seen as a high-risk asset. Only buy enough bitcoins to make convenient online purchases.[15]
Anti-money laundering (AML) and know your customer (KYC) practices have a strong potential for being adapted to the blockchain. Currently, financial institutions must perform a labour intensive multi-step process for each new customer. KYC costs could be reduced through cross-institution client verification, and at the same time increase monitoring and analysis effectiveness.
A prospective miner needs a bitcoin wallet—an encrypted online bank account—to hold what is earned. The problem is, as in most bitcoin scenarios, wallets are unregulated and prone to attacks. Late last year, hackers staged a bitcoin heist in which they stole some $1.2 million worth of the currency from the site When bitcoins are lost or stolen they are completely gone, just like cash. With no central bank backing your bitcoins, there is no possible way to recoup your loses.
Nakamoto is estimated to have mined one million bitcoins[27] before disappearing in 2010, when he handed the network alert key and control of the code repository over to Gavin Andresen. Andresen later became lead developer at the Bitcoin Foundation.[28][29] Andresen then sought to decentralize control. This left opportunity for controversy to develop over the future development path of bitcoin.[30][29]