Goog a Yahoo also seem to have lower bogus rates--it apparently goes as high as 27% for smaller PPC engines. [msnbc.msn.com...]
"Google says its technology manages to recognise many of the bogus clicks. It does not charge advertisers for them or later grants them refunds.
But the Outsell media research firm said this month that its survey of more than 400 advertisers showed that on average they still felt 14.6 per cent of the clicks they were being billed for were fraudulent."
