Only some billing models are vulnerable to fraud though. The old school "your ad here for 2 weeks for this price" is not vulnerable to it since you're no longer charging per click/impression.
The "measurement function" becomes the uptick in sales resulting from the unique link embedded in said ad and ultimately the money that lands in the bank.
The "measurement function" becomes the uptick in sales resulting from the unique link embedded in said ad and ultimately the money that lands in the bank.