A lot of my accounts (friends + family also) have also been hit with Economic exploitation. I wonder what triggers it. I'm stingy, I don't give out gold.. - don't even move it around lol.

@op
You should be able to get them unbanned if you really didn't buy/sell gold. Although they might just slap an account sharing ban then.. idk. You can always prove you and your gf own the accounts though :P