OK, I open up my Adlogger and I see all IPs, suddenly I notice that a guy from same IP and clicked two ads, one after the another... Is it just common, or should i report it back to Google ?
That's not anything that is going to raise a flag in their system. If you start to see 4, 5 or more clicks from the same IP a couple days in a row you could edit your .htaccess file and ban them but being overly cautious and sending emails to Google like a mad man could actually do you harm. If people click your ads too fast, they don't count them anyways. It is Googles job to identify invalid clicks. The purpose of Adlogger is to give you proof incase Google does ban you, but more importantly it gives you the power to identify abusive visitors and ban them before it even escalates to a major problem.