This is something that should be tested by APCW for verification.
While this is only my experience, I have done very well with GSN ever since Marlo left and even now their performance is outstanding in terms of revenues being produced. As I reported previously earnings at a few other MGS groups I work with basically went off a cliff in February and March (CPS, Roxy and Casino Rewards) that DIDNT happen at GSN, so for me they have been one of my few bright spots these past two months.
I have never had any reason to believe there was a problem with tracking based on the level of exposure I give them and the subsequent monies generated. I havent tested it though so I think you guys should get J Todd to look into this.