I have used Adbrite for their flat rate ads successfully, but I wanted to better target consumers so I signed up for a CPC deal using keywords. Reviewing the logs I notices that most of the clicks where coming from "Pay to click" sites in China where unethical publishers pay their subscribers to click an advertisers site. The other site where the clicks came from was a Warez and Ad-ware site.
I have tried it a few times (maybe 2,000 or so clicks) and have never gotten a signn up on what is normally a 30% conversion free forum site.
I thought Ab-Brite banned those pay-to-click sites. I dont think any Advertising Network is ammune to some level of click-fraud. But where they dont even take minimum precautions is a bad sign.
I tried to buy some ads on Adbrite, but the publisher denied my purchase saying that the set price was "too low." so that's strange
take back what i said about albrite, he didnt use the 'network' feature, but bought ads on individual sites, in fact bought many. and if they converted well, call or emailed the site owner to work outside of abrite, lol.