Something interesting at the same time irksome caught my eye this morning. Published on the Inside AdSense weblog is this:

Accidents happen
As most of you know, our program policies state that publishers are not permitted to click on their own ads for any reason. For this reason, we've received many emails from publishers letting us know that they've accidentally clicked on their own ads. If you're one of these publishers, we truly appreciate the efforts you've made to monitor your account and keep it in good standing. However, we do understand that an accidental click may occur from time to time, so there's no need to contact us each instance this occurs.

Because we closely monitor all account activity using engineering systems and thorough human analysis, chances are we've already detected your clicks on your ads and discounted them. While these clicks still show in your reports, we filter out their associated earnings so that advertisers aren't charged. However, please keep in mind that we don't ignore the clicks completely; if it appears to us that a publisher has been clicking on his own ads to inflate his earnings or an advertiser's costs, we may disable the account to protect our advertisers' interests.

Now, the question is: How does the search engine giant know if it was the blog owner who clicks on the ads to automatically impose a credit? How is Google to know the click was accidental?