I'd have to say that probably 99.9% of the people on this forum are not "sponsored" But i don't see anything wrong with using a sticker for say an organization that helped you get your car to where it is today.
Personally, i don't like putting stickers on my car, however, i have put only one sticker which represents the crew that did all the mods to my car. They did good work, so i have no problem advertising for them.
As far as stickers from random manufacturers that didn't lay a hand on your car, well, to each their own.
