I've been sitting on about $500 in my CJ account for a couple months now, I figured it's not a lot of money and I can get to it later, not smart I know. But anyways, the reason I don't have the money is because I haven't sent them back the tax form they sent me when I signed up. I'm starting to think that's the reason I keep seeing my balance there decrease. It went from 480, to 420, to 360, and now it's about 280. Are they going to keep pinching me if I don't send in this form, or are advertisers getting their money back? Either way I think it's pretty dirty of them to take their money back, does it hurt them at all for them to hold it?
You do not need to send the tax form. The most probably cause of these drop in your balance is that some of your sales are getting reversed (invalid credit card, returned sale... no sale = no commission) - run a detailed report for the period and you will see the reversed sales in red and - you can also contact your advertiser for further information about the reversals.
The only time CJ threatened to take away money was when I went through a period of no sales. I think Micromag has the right answer.