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.
In 2013 and 2014, the European Banking Authority[145] and the Financial Industry Regulatory Authority (FINRA), a United States self-regulatory organization,[146] warned that investing in bitcoins carries significant risks. Forbes named bitcoin the best investment of 2013.[147] In 2014, Bloomberg named bitcoin one of its worst investments of the year.[148] In 2015, bitcoin topped Bloomberg's currency tables.[149]
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%.
“While it’s still fairly new and unstable relative to the gold standard, cryptocurrency is definitely gaining traction and will most certainly have more normalized uses in the next few years. Right now, in particular, it’s increasing in popularity with the post-election market uncertainty. The key will be in making it easy for large-scale adoption (as with anything involving crypto) including developing safeguards and protections for buyers/investors. I expect that within two years, we’ll be in a place where people can shove their money under the virtual mattress through cryptocurrency, and they’ll know that wherever they go, that money will be there.” – Sarah Granger, Author, and Speaker. 
Bitcoin mining operations take a lot of effort and power, and the sheer amount of competition makes it difficult for newcomers to enter the race and profit. A new miner would not only need to have adequate computing power and the knowledge to use it to outcompete the competition, but would also need the extensive amount of capital necessary to fund the operations.
Two members of the Silk Road Task Force—a multi-agency federal task force that carried out the U.S. investigation of Silk Road—seized bitcoins for their own use in the course of the investigation.[68] DEA agent Carl Mark Force IV, who attempted to extort Silk Road founder Ross Ulbricht ("Dread Pirate Roberts"), pleaded guilty to money laundering, obstruction of justice, and extortion under color of official right, and was sentenced to 6.5 years in federal prison.[68] U.S. Secret Service agent Shaun Bridges pleaded guilty to crimes relating to his diversion of $800,000 worth of bitcoins to his personal account during the investigation, and also separately pleaded guilty to money laundering in connection with another cryptocurrency theft; he was sentenced to nearly eight years in federal prison.[69]
Americ, your insights were very informative! A few months ago I didn’t even know what blockchain is, only heard about cryptocurrencies. My friend suggested me to start an investigation on crypto-mining, there was a boom of articles, but in most cases highly generic ones. Thus my friend found BitDegree publishing lots of good stuff about the crypto world, and especially the whole tutorials about mining that helped us to our Litecoin mining career step-by-step!
Though transaction fees are optional, miners can choose which transactions to process and prioritize those that pay higher fees.[68] Miners may choose transactions based on the fee paid relative to their storage size, not the absolute amount of money paid as a fee. These fees are generally measured in satoshis per byte (sat/b). The size of transactions is dependent on the number of inputs used to create the transaction, and the number of outputs.[3]:ch. 8

Though each bitcoin transaction is recorded in a public log, names of buyers and sellers are never revealed – only their wallet IDs. While that keeps bitcoin users’ transactions private, it also lets them buy or sell anything without easily tracing it back to them. That’s why it has become the currency of choice for people online buying drugs or other illicit activities.
Predictious.com is a betting websites that matches buyers and sellers and doesn’t price the options themselves. Besides betting on bitcoin’s demise or rally, you can also try to predict the next winner of the Oscars or bet on which party win control the US Senate after the 2014 elections. Currently the site takes bitcoin deposits only. Predictious does accept US clients.
What's more, unlike traditional arbitrage play, the inherent volatility of the BTC market all but forces investors to offload their coins as quickly as possible to avoid getting caught in a crash. However only when investors hold onto their digital commodities for longer periods of time will the market actually stabilize. It's a catch-22. And without commercial institutions like banks, which have huge reserves of liquid capital they can rely on, individual investors often can't afford to just sit on their Bitcoin and wait for a rainy day.

According to the Library of Congress, an "absolute ban" on trading or using cryptocurrencies applies in eight countries: Algeria, Bolivia, Egypt, Iraq, Morocco, Nepal, Pakistan, and the United Arab Emirates. An "implicit ban" applies in another 15 countries, which include Bahrain, Bangladesh, China, Colombia, the Dominican Republic, Indonesia, Iran, Kuwait, Lesotho, Lithuania, Macau, Oman, Qatar, Saudi Arabia and Taiwan.[167]
What’s so special about Bitcoin? There are many arguments on whether the new virtual currency will succeed or fail. We will not get into this nor discuss the politics behind the project. Our concern is strictly with the profit opportunities provided by this new payment phenomenon. In the next few pages on the new digital currency we will outline our thoughts from the perspective of a trader and a potential investor in this upcoming market.
Coinbase is probably the easiest and safest way to purchase bitcoins in the U.S. Unlike BitStamp, Coinbase is not an exchange. They act as a counter-party to all customer trades, you buy or sell your bitcoins directly to Coinbase. The buy/sell fee is 1% on top of the buy/sell spread. The bid/ask is usually close to BitStamp where the firm gets its liquidity from. For example, the current bid is at $635.48 and the current ask is $638.07. In addition to this, the firm has daily limits on the amount of bitcoins bought/sold. These limits are not applied on the individual level. Basically Coinbase has a set amount of bitcoins that it is willing to buy or sell every day. During times or high volatility, users may not be able to buy/sell bitcoins until Coinbase decides to ‘’refill’’ their stock. Here’s a good explanation on this issue from their Customer Support:
Though transaction fees are optional, miners can choose which transactions to process and prioritize those that pay higher fees.[68] Miners may choose transactions based on the fee paid relative to their storage size, not the absolute amount of money paid as a fee. These fees are generally measured in satoshis per byte (sat/b). The size of transactions is dependent on the number of inputs used to create the transaction, and the number of outputs.[3]:ch. 8
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