It's a bit more complicated than that. Right now, you have to file for every bank account you own (or have signature authority for) if the combined worth is more than $10,000. So it's not as bad as I wrote at first, and I appoligise for that, I had forgotten about that factor. But it still surprises people.

Edit:

Oh, and the worth is calculated as the maximum value during the year. So if you get a contract filled for $10 000 and someone wires you the money, even if you imediately pay the rent and therefore have no money in the account, you still have to report the account.