You're right, it's not impossible. Not only that, it's pretty common. At the beginning of February, the dollar was at about 122 yen and by the end of that month it was at about 115. This was about a 5.7% drop in a month.
Traders that max out their leverage say at 100:1 can only stand a 1% drop before they're wiped out. Even someone with a smaller position size who's only using 10:1 leverage would have experienced a 57% drop in their account value.
I figured this would make a great AIM candidate because it's volatile and currencies don't "go to zero" like a stock can. But to make AIM work for FOREX you would have to cut down the leverage a lot. This eliminates the benefit of the interest rate spread on the carry trade.
Market Data 
Markets 
AI
