I agree with you and ChrisMarshallNY, I think both can be true. I have a work laptop and personal laptop that would be identical if not for stickers, but at the same time I enjoy stickers because they lend personality to something that would otherwise look the same as every other one; I'm sure signalling plays a part for some people, but mine are all novelties.

Maybe, but I always assumed that it was for the same reason that people put them on their cars.

They are really signals to others.