Interactive Brokers - I've had to deal with that quite a few times. It's irritating as hell, especially when they drag their feet lifting the trading restriction, and you have to call them after you have already let them know that you're not an affiliate. I've even had it happen when I was holding short positions in some thinly traded stuff. Mind boggling really.
Interactive Brokers has some really good features, but they seem to be over the top on the regulatory stuff compared to other brokers.
I have seen lots of $1 stocks with strong earnings and solid balance sheets triple, quadruple and more, but I have yet to see one go below zero.