Gotta disagree with you there Brett. They are saying 10% of clicks are invalid or not chargeable. Not necessarily refundable because most are filtered at source and never charged anyway.
When I get stung on PPC fraud it is a) rare and b) painful. But mostly it is a) rare and b) insignificant.
Most "PPC fraud" is actully dumb PPC managers bidding on broad match.
[added]we don't use content match much, I'm afraid... so I can't comment on that, except that it sucks for conversions[/added]
[edited by: Receptional at 2:31 pm (utc) on Mar. 1, 2007]