People can do "click-bombing" but as far as I know, Google knows the difference. I think Google is cracking down on MFA-type sites. There could be any number of reasons for the ban. Maybe he used his keywords too many times. Did his sites have informative helpful content? Probably the best thing he can do is make his sites as informative as possible. Become an expert on the topics. There are other income streams besides Adsense - Amazon, Clickbank etc. He could write an e-book and sell it on his sites.