Poloniex was once the best cryptocurrency exchanges, before competitors like Bittrex starting offering superior services. Nevertheless Poloniex went through extremely fast traffic growth since the demise of its rival Cryptsy in 2016, and especially since the recent altcoin bubble of early 2017. Traffic has grown from 33 million monthly visits in November 2017 to 66 million in December 2017. Poloniex has the nicest trading interface out there, both for mobile and desktop users this will work wonders. Please note that because Poloniex is a pure "crypto" exchange, it is not possible to deposit government (fiat) currency. You'll need to first buy bitcoin elsewhere, and then deposit it to be able to tade. I've written a full analysis of Poloniex, further exploring the founders, users, security, fees, history, and alternatives.
The picture above shows some of the recent large transactions recorded in the block chain. The first transaction is for 205 BTC, the equivalent of $187,165 at today’s prices. The long lines of letters and numbers you see in the pic are bitcoin addresses. A bitcoin address consists of 27-34 alphanumeric characters, beginning with the number 1 or 3. You can have as many addresses as you want, they’re free and easy to generate.
“If the trend continues, the average person will not be able to afford to purchase one whole bitcoin in 2 years. As global economies inflate and markets exhibit signs of recession, the world will turn to Bitcoin as a hedge against fiat turmoil and an escape against capital controls. Bitcoin is the way out, and cryptocurrency as a whole is never going away, it’s going to grow in use and acceptance as it matures.”
Despite the fact that your bet on British pounds earned you an 11.11% profit (from $1,000 to $1,111.11), the fluctuation in the bitcoin to U.S. dollar rate means that you still sustain a loss of .016 bitcoin, or -0.8%. (initial deposit of 2 bitcoins — 1.984 bitcoins = .016 bitcoin). However, had the bitcoin to U.S. dollar exchange rate changed to 1 bitcoin = $475, you would realize a profit from both the forex trade and the bitcoin exchange. In other words, you would have received ($1,111.11/$475) = 2.339 bitcoins, a profit of 16.95%.
A lot of you have asked me whether trading bitcoin is better than buying it. The answer depends on your goals, and experience of bitcoin trading. If you're looking to hold bitcoin as a long-term investment and check the price intermittently, it's better to buy bitcoin. This way you benefit from a small, one time exchange fee and the assurance that you hold a physical bitcoin in your wallet which can be spent at various retail stores.
Bitcoin has been criticized for the amount of electricity consumed by mining. As of 2015, The Economist estimated that even if all miners used modern facilities, the combined electricity consumption would be 166.7 megawatts (1.46 terawatt-hours per year).[130] At the end of 2017, the global bitcoin mining activity was estimated to consume between one and four gigawatts of electricity.[203] Politico noted that the even high-end estimates of bitcoin's total consumption levels amount to only about 6% of the total power consumed by the global banking sector, and even if bitcoin's consumption levels increased 100 fold from today's levels, bitcoin's consumption would still only amount to about 2% of global power consumption.[204]

The idea of not needing a third-party exchange can admittedly be a tempting one, especially if you're worried about how secure they are. But direct trades come with plenty of risks, too. By putting you directly in contact with the buyer, they leave the method of trading up to you, including potential in-person exchanges, which are incredibly risky to do with a stranger. Some of these methods can also be annoying, frustrating and more time-consuming than preferred, and if a buyer is unreliable, it can take even longer should you end up successfully selling them at all.

To understand the revolutionary impact of cryptocurrencies you need to consider both properties. Bitcoin as a permissionless, irreversible and pseudonymous means of payment is an attack on the control of banks and governments over the monetary transactions of their citizens. You can‘t hinder someone to use Bitcoin, you can‘t prohibit someone to accept a payment, you can‘t undo a transaction.
BTC-E does accept US clients. However, starting from the middle of December 2013, the company stopped processing US dollar wires or any wires connected to a US bank. Here is an email reply to a customer’s question on this: ‘’We don’t accept international wire transfers from US Citizens or from US Banks. All transfers from US Citizens or US Bank will be refused by bank.’’
“Trading bitcoin is like trading anything else on an exchange. You can trade dollars for euros through forex, and dollars for bitcoins on the exchanges. It’s very similar, but it depends on the idea that it’s traded on an actual currency,” said Lord. “There’s a little bit of a disconnect when talking about it. It’s not a real thing. There are many who say it is a currency, but it’s not as dynamic as trading currencies.”
Cryptocurrencies have been compared to Ponzi schemes, pyramid schemes[77] and economic bubbles,[78] such as housing market bubbles.[79] Howard Marks of Oaktree Capital Management stated in 2017 that digital currencies were "nothing but an unfounded fad (or perhaps even a pyramid scheme), based on a willingness to ascribe value to something that has little or none beyond what people will pay for it", and compared them to the tulip mania (1637), South Sea Bubble (1720), and dot-com bubble (1999).[80]
Transactions are verified by network nodes through cryptography and recorded in a public distributed ledger called a blockchain. Bitcoin was invented by an unknown person or group of people using the name Satoshi Nakamoto[9] and released as open-source software in 2009.[10] Bitcoins are created as a reward for a process known as mining. They can be exchanged for other currencies,[11] products, and services. Research produced by the University of Cambridge estimates that in 2017, there were 2.9 to 5.8 million unique users using a cryptocurrency wallet, most of them using bitcoin.[12]