It's always unwise, but especially so when you have government actors (like, for instance, the Japanese Central Bank) willing to come in and break every rule in the book (which they're immune from, of course) to screw you.
If you're wondering how bad that could have been it's about $5,600 margin to trade one contract, but each TICK (0.0001) is $12.50.
That was 259 ticks for the duration of the squeeze in a little less than two hours, or $3,237.50. If you were short one contract you lost about 60% of your margin in less than two hours.
This is a grand way to blow your account to bits, if you're nuts enough to get involved in such a thing and not be continually watching it.
Impressive stuff, and once it got going it fed on itself for a while too, no doubt having been strategically initiated right about the time the margin clerk starts looking at things.
It's great to be able to manipulate markets with a license from a government, eh?
This looked like it came out of Japan originally, although it's not certain, and it also looks like the Swissys got involved around 12:30 (Central). Heh, who knows - maybe it was Geithner - or Bernanke!
We do audit The Fed to check on stuff like that, right? Oh wait....
Gotta love those "free" markets....
PS: It didn't do all that much for the equity markets. These folks should know that tampering with FX like this is dangerous due to the leverage inherent in the trades, and that it hurts real producers who find it impossible to hedge foreign product and service sales when this sort of violence is being served upon them on a daily basis, and has a decent chance of potentiating a crash rather than "stabilizing" things.