This is what I think, not really that I know exacatly, and I hope they are thorough in this.
Cross-referencing that data with my website access logs also showed that there were more direct referrals from my AdSense ads than I'd been charged for, so clearly Google considered some of them invalid.
[edited by: SteveWh at 10:16 pm (utc) on June 27, 2009]
I do know some ad platforms that filter out anything over 3 clicks from the same ip in 24 hrs and i know others that allow as many as 5. I also know of one company that only allows clicks from unique ip #s every 24 hrs.
Maybe this thread will provide more insight into filtering repeats.
Thanks
Slim