the click-bots might be repetitive page requests from the same IP address, but a devious click-fraudster would use a zombie network, which would be more difficult to detect. a pay-per-ad-click system would be susceptible to the same vulnerabilities as a pay-per-page-view system, but the latter is more beneficial to the submitters IMVHO. the worst-case scenario would be repetitive page requests from the same IP address that submitted the item to sharecg.