Rightly or wrongly, since I've been on AB, I've not come across a professionally qualified scientist who treats Wikipedia with any authority. The reasons? Well it's exactly as jno said.
The truth is that once you allow any Tom, Dick or Harry to edit what's intended to be a reasonable authoritative resource for the public, all sorts of things happen. A while back, Wikipedia had to stop the article on George W Bush being editable because of the abuse and tripe that was posted. It hasn't been the only one:
http://en.wikipedia.org/wiki/Wikipedia:Most_va ndalized_pages
Once the damage has been done, Wikipedia has to rely on genuinely qualified and/or knowledgeable people to rewrite part or all the article to put it right. This can be happen in hours, weeks or months depending on when it's noticed, but the problem is that in the meantime someone else might be reading a load of tripe.
On the other hand, a review in the Daily Telegraph some months back put Wikipedia slightly ahead of the online version of Encyclopaedia Britannica in terms of reliable knowledge, with I think, Encarta in third place, so it's not all bad.
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