> anyone in a grocery store would guess.

Actually, I'd challenge that particular point.

Mushrooms seem to be found in the fresh fruit and vegetables area, rather than in the deli (meat and cheese), so that would probably point more towards them being considered "vegetables". Or fruit. ;)

Yep, however one wishes to classify them botanically, mushrooms are a vegetable in culinary usage (similar to tomatoes in that way).

I agree. Sorry, bad English. "as" -> "in oposite of" (or something like that).