What temperature are dark beers (stouts and nut browns) supposed to be consumed at? I remember reading somewhere that certain beers are supposed to be drunk much closer to room temperature than most people drink them for optimal flavor.  Specifically stout beers and nut brown ales are only supposed to be "slightly chilled".  I think I read that the temperature for optimal flavor is around 55 ℉ (13 ℃).  However, most people I've met are shocked when I tell them this and swear by a nice cold one.  My own personal experience does seem to confirm the "slightly chilled".  Am I crazy?
No, you're not crazy.  You have good taste.  The reason for drinking darker beer like stouts and porters is for the flavor.  If they are over-chilled, you lose most of that flavor.  Don't obsess over it, but in general a lot of people serve dark beer too cold.

That said, you should drink your beer at whatever temperature makes you happy. There is nothing wrong with a nice cold pilsner or Hefe-wizen on a hot day.