Yes. There's a good reason too (when a source is freely editable).
I work with with professors and other research students at University, and we've spoke about using Wikipedia before. They generally think that Wikipedia has two main pitfalls with it being editable.
1. It can contain dubious information.
2. It can contain useless information.
People can hack and change the information freely. I know I've seen some things that I've thought are dubious and generally wikipedia are very good at staying on top of this.
But Wikipedia are not on top of people writing superfluous information. I've read a few wikipedia articles on subjects I know well (mostly out of curiosity) and thought that much of the information is superfluous and could be removed without damaging the article at all.
People are always well aware of the information potentially being false. But people don't generally know about the other end of the scale in that the article can contain irrelevant information, which is not good if you don't need to cover a subject in too much depth.
You need to build an understanding from other sources (preferably books, papers and other published material) because only then will you realise what is important and what is not, what needs to be included in your work and what doesn't.
If you read an article on wikipedia and use that as your main source, then you run the risk of including the same mistakes, but also you run the risk of using superfluous information because you believe it to be important because, hey, it's on Wikipedia.
It's reflected in the students work when you see they've fallen into this pitfall. Personally I think the latter should be emphasised more, it's rarely as covered (maybe because the potential for mistakes has more impact).
