Google makes money off its 500 million queries a day, less then 1% of its revenue comes from the top 100 most popular queries. Assuming some big even company has just given you unlimited money and told you to mass defraud google what would you do? 1.You would have to replicate the browsing habit of 94 million google users, down to the geo distributed IP address and user agents etc. 2. You have fake user agents, and language etc, you have to find out what the random click distrubution pattern is across the web and then replicate that randomly. 3. 13% of all my traffic is infected with ASK jeves spyware. How much of internet traffic has the google toolbar installed? How will you replicate that the traffic to google. 4. The only feasible solution currently are clickbots from hundreds of thousands of infected computers, but that is trivial to spot if its being used for personal profit. If its being used as a attack on googles revenue stream its a bit harder but not much. At any rate, I was invited to the googleplex and had a mini speak/Q&A session with 20 some engineers. We talked about clickfraud and i preseted a bunch of ideas to combat it. I really isn't much of a problem, then again they offered me a job at least 3 times before i got out of there lol. The larger issue is that because computers are slow and browsers messed up, around 30% of all clicks are garbage because they have been reported more then once. Just use the free tracking script for adsense and install it on your pages. You'll be amazed when you look at the stats.