Honest answer - most programs have shaving. Not all of it is intentional, while other is very much intentional, and can be everything from traffic leaks to direct shaving. Ex. If you look at the AEBN program who ownes xpeeps, then your refer ID is not used/credited, if a studio was to find AEBN using your link/refer code (you do not get a cut from the businessies - only the surfers). Also there is a leave link (under 18), which goes to google, 2257 link to asacp.org, and a certificate link to truste.org - those would be a traffic leaks, which you are not getting credit for, but where real visitors might end up.
Overall a % of surfers also loose their refer codes, so you will not get credit for those. Depending on the ways the site tracks, then it could be minimal or substansial. More tracking ways = better tracking. The best outthere have 4 (hardcoded urls, browser cookies, server cookies/sessions, and even manual submitform entry of refer id). On the AEBN sites I could find 2 out of 4.
Then there are also the entire lose of tracking once the processor is handling the transaktion. This can also be minimal or substansial depending on the processors. If its a 3rd party processor in use, then you can ask around, and hear what other webmasters are saying. If its an "inhouse" solution, then you have to trust that the program will count everything on the processing side. AEBN is using their own inhouse solution.
So as you see even the biggest sites out there are in the shaving dilemma - some of it they can control other is more difficult. And that is an honest answer
