Some people would be annoyed by anything that looks like advertising. I don't think it's a big deal, so long as you leave *one* per cache, and not a whole stack! It might depend on exactly what the sticker says as to how it is perceived.
Thanks Buckeye, in thinking more about it, I'd rather not see stickers start to make their way into caches, unless they are individually thought out and each unique. If I were to put one of my businesses stickers in a cache, it would probably best be put in a cache very far away from my local area..
Better to keep business and pleasure separate. Thanks for the reply!