I think its a great source and would use it for citation in a heartbeat. **** what scholars say. The only reason teachers prohibit it is because its convenient and easy to access. They like students to bend over backwards to complete their ****ty assignments. Unfortunately for me, Wikipedia hadn't fully blossomed when I was in high school. I discovered it after I graduated.
For those unhappy with Wikipedia, the co-founder has created a new one called Citizendium which strives to use "gentle expert oversight" and require contributors to use their real names".
http://en.citizendium.org/wiki/Main_Page