When I started this topic almost 2 years ago, Bitcoin had already taken off and those who had profitted the most were the ones who started mining (performing calculations to generate coins) with CPU's when Bitcoin started in 2009 and a Bitcoin was worth only a couple of cents. Bitcoin by the time this topic was started was being mined with GPU's, mostly AMD/ATI GPU's, because they are better at OpenCL GPGPU computing (do not confuse it with OpenGL, the graphics API used by ET, at which AMD/ATI cards suck because of bad drivers). They were then worth around US$ 3 per Bitcoin.
Now, those who always hear and obey
The Sacred Emperor and either started mining in 2011 or bought Bitcoins through exchanges, saw Bitcoins rise dramatically in price a few weeks ago, and peaking at US$ 266 per Bitcoin, when the bubble burst and the price went down to today's average of US$ 70 to US$ 100. People who follow the market closely and cashed out during the bubble literally made millions. New bubbles are expected soon though because of all the attention Bitcoin has been attracting from the media lately (hint! hint!). For you to have a better idea of the magnitude the digital currencies market has reached, these are today's statistics for the main Bitcoin forums at
www.bitcointalk.org: 1,777,759 Posts in 108,090 Topics by 98,741 Members. In the past 24 hours, the volume of Bitcoin trades realized on the main Bitcoin exhange, Mt.Gox (also one of the worst), was 419,522 BTC, or roughly 29,366,540 USD at current exchange rates - and that was a slow day.
Mining Bitcoins with GPU's nowadays is nearing the point of being unprofitable because of the huge increase in the difficulty of the calculations needed to generate the coins, with many miners using FPGA devices and eagerly waiting for the first dedicated ASIC mining devices to start being delivered to the market. There are other alternative cryptocurrencies that are still profitable to mine with GPU's though, which may be traded for BTC or USD at exchanges.
Below are two very well written articles published on the current edition of the magazine
The Economist:
Mining digital gold - Even if it crashes, Bitcoin may make a dent in the financial world
A new specie - Regulators should keep their hands off new forms of digital money such as Bitcoin