Approximately 25 percent of large companies that are exposed to foreign currency fluctuations don't do anything to hedge their risk. Larger companies however do hedge in the currency markets.
For an US based company, when the dollar is strong during their reporting period, accounting for its foreign earned revenue can result in a negative performance. That's because foreign-currency denominated revenue will exchange for fewer dollars when converted and reflect negatively for the accounting period.
It has been estimated that 5-10% of the activity on the FORX market is done because of business hedging and government involvement. Governments and businesses need to convert one currency into another to buy and sell goods and services. The other 90-95% is pure speculation.
The foreign exchange markets have been the playground of governments, corporations, banks as well as high-profile traders such as Warren Buffet and George Soros. Many speculators have made consistent net profits. For instance, George Soros "broke the Bank of England" by shorting the pound and walked away with a cool $1-billion profit in a single day.
Since the currencies are traded 24 hours there are certain times that are more liquid than others for the various currency pairs. For instance, between the hours of 8 AM and 5 PM EST, New York accounts for about 15% to 17% of all FOREX transactions. On the other side of the globe, 10% of FOREX transactions take place between Tokyo's trading hours from 7 PM to 3 AM EST