Sevin - 12:00 am on Jul 20, 2011 (gmt 0)
My account stopped running at one point. When I sent a message asking why, I got a phone call that day and they explained that too many of my landing pages had popups. I removed all the popups and let them know about, and my account starting running again the next day.
So yeah, I've had some problems, but at least they don't ban your for life like Google does.