Sorry if this is reviving an old thread, but I just found this forum and really wanted to add something.

Wikipedia is a great place for general knowledge and finding links to other sources, as has already been mentioned. However, I think the main reason it is unacceptable as a reference is the fact that Wikipedia articles have not been peer reviewed. Imagine submitting a paper to Nature (for example) with a Wikipedia reference. That would not fly, and I like it when profs adhere to the same standards as the rest of the scientific community.