I'd rather see things on the MU*. Honestly I feel that wiki's have killed a lot of what our hobby is, not enhanced it.
Does anyone even look at desc's anymore? My favorite is someone not looking at the desc of a police PC, who was clearly desc'd in uniform and did not have a wiki yet. Someone was stupid in front of said cop PC and then freaked out OOC because "I had no way of knowing you're a cop".
Nothing is secret because, well, wiki. There's no sense of wonder, it's hard to enjoy that suspension of belief sometimes because everything is on the wiki about PC's.
I'm not completely anti-wiki. If you have a lot of theme stuff, background story etc etc as a game. Then a wiki is great for that. Take Arx for example, massive amounts of lore and things to know... NO SEARCH FUNCTION.
Wiki's make for a good friendly way for new folks to view the game, absolutely. You know how to log in the game, maybe a chargen guide is up. Things like that are not so bad.
For the most part, it's just simpler to keep it all in game. Oh, and well, less bots posting dumb shit on a MU*, unlike wiki's.