I too after months of fabulous PPC was told my account was suspended over 3 domains, 3 of 100's!!!! I was given no noticed just a 100% cut off. Funny I searched the traffic on them to find no real suspicious activity myself, only slightly higher clicks. On 3 of 100's, I thought to myself what the hell, take that revenue back and let me continue as I have been satisfied. Nope no can do, good bye! I was disheartened. And personally believe their over reacting for no reason several times over.
I never knew they gave warnings? If I did I would have protested.