Conclusions

Forex trading is a high-risk, high-reward pastime. Fortunes are made and lost every time a currency changes value. The small investor is at a disadvantage compared to the major institutional banks for two major reasons: wider spreads and under-capitalisation. The consensus amongst the professional traders is that somewhere between 80 and 95% of day traders lose money and even the majors get in to trouble on occasion. In 2002, Allied Irish Banks revealed that it lost US$750 million at its Baltimore subsidiary on spot and forward forex trades made by forex trader John Rusnak and in 2003, the National Australia Bank admitted to losses of US$1.13 billion as a result of unauthorised forex trades, although it seems any time a bank loses money, it's a result of "unauthorised," activity.
Realistically, a private individual should only enter the forex market with a bare minimum of $10,000 "risk capital," i.e money that can be lost without causing hardship, and a good understanding of the mechanisms of the market. The nature of the forex market means that the smaller the sum risked, the greater the price fluctuation needs to be before a position becomes profitable. This doesn't mean it is not possible to make money trading foreign currencies, CitiGroup would not be interested if there wasn't an awful lot of money in forex trading, but it's not necessarily as easy as some would have you believe