FourDegreez - 1:02 am on Mar 2, 2007 (gmt 0)

A simple (and hypothetical) example of a "grey area" click incident might be two clicks in rapid succession, which could occur if an impatient user clicked an ad twice while waiting for a response. The second click might be "invalid," but it wouldn't be fraudulent.

I would imagine this is relatively common, as may be other common behaviors that Google may not "count". To paint all such clicks as "fraud" is a gross misrepresentation. From the quoted article:

Cases of provable click fraud attempts constitute a small minority of the clicks we mark as invalid.

And furthermore, probable or possible click fraud attempts consistute another portion of the 10%. The rest of the 10% is rounded out by garden-variety junk clicks. In any case, none of these clicks are charged to advertisers, so I can't see how anyone would read this and take it as evidence against using the content network. It looks to me like Google is over-cautious in not charging on clicks if there is any reason to suspect those clicks aren't legit.