There are a lot of non-UX tags in our tag-wiki and we need to think why they exist. Users (with the privilege) create tags by themselves to sort information among these 5000+ questions. A tag being used on five or more questions is relevant in some context (maybe not UX, but on another facet).
Still, questionable company and company-feature tags are around in our tag wiki. Like the following (non-comprehensive) list:
google 22, google+ 9, android 126, facebook 20, facebook-connect 7, apple 9, mac-os-x 22, iphone 108, windows 27, windows-os 16, windows-phone-7 14, windows-8 8.
The Windows tag is noted by the DO NOT USE wiki, but I doubt it has the desired effect.
I think we should be very careful if we’re going to change or remove tags, especially if they are used a lot. They will most certainly come back leading to the doubtful work to sort tags out again and again. I think the best option is to leave them as they are, since it helps our users to sort questions (and answers).