Please understand mpov:
The problem is when a certain player either completely ignores the guidelines the DM has given them, or, fails to inform the DM. As always communication is key. It isn't a one way street (communication), and it isn't just the DM, when a player is given guidelines, and completely ignores them. The powergamer seeks to exceed campaign expectations (both that of the other players and the DM) with regards to concept, and will argue for the inclusion of rules (PrCs, races, feats, and so on) in order to achieve a level of power above and beyond what is "normal" and accepted by the group. If a group has a higher tolerance level of power in their campaigns, good for them. That isn't a problem. It all comes down to player expectations.