as long as it did not have pop ups it never bother me. This is pretty much a stretch for Apple to call that cheating the system. Hell I found some fun games by going an offer wall in another one of hte games.
There's a big difference which you're not getting.
Tapping on an iAd doesn't benefit the user in any way. If they're tapping on it, they want to look at the ad and then potentially buy the app. You're only downloading the app if you actually want the app, so it seems right that this counts towards the download charts.
If you're tapping on an offer on the offer wall, you're only doing this to gain points/currency/XP inside the game you're playing. You're not downloading the app because you actually want it, it's simply a means to a very different end. Why should this boost the app in the charts?
Offer walls treat apps like currency, iAds treat apps like apps