For those not around when IOI used to post on GAF:
He got a bad rap because he would make claims he never would back up. ie most of his numbers. I'm not the official word on this but have been around gaf and the resultant sales age. From what was percieved, he was just another poster with no ties nor contacts to get these types of numbers. NPD is just another tracker but they have methods that are divulged. How does IOI get his numbers? Nobody knows. Maybe he thinks it's a trade secret but if you don't know the source, how can you be sure?
Could he ever prove that his numbers are legit? I haven't been to this website for awhile but it's not the case where people hate IOI just for the hell of it. They just didn't like him making up numbers w/o any sources. There is a hell of a community on GAF that tries at guessing at these numbers and never pretends to be anything but guesses. For the most part, people saw IOI as a big guesser who has made his site into something more.
Why would he do that? I don't know and all my reasons would be guesses. But I remember a big defense IOI put up was that his site was simple, didn't involve finances etc. Now, I can't move on this site w/o seeing an ad. But I'm just making a guess.
