its a very informative article ,ya i agree with your all points ,now some people adopting another trick they first trying to get keywords on which their site showing in search engine.then they are telling their friends to follow that path to click their ads ,but i dont like one method of Google is if some body has enmity with another user and that user started clicking everyday the result will be ban of that innocent user's account.But adbrite filters all invalid clcik they dont count these.Gogle always search for excuses how to ban or delete account.