Well, tbh, as long as it doesn't spoil the fun or the ads that add more realism towards a game (as long as it looks natural), why not? But some games shouldn't get ads when it would be misplaced if there were ads in it.
I do agree that lowering prices would be enjoyable too, but I reckon we can all forget about that since that really will not happen....
The Patapon forumtopic: http://www.vgchartz.com/forum/thread.php?id=14103