Yup, apparently they do. I think the look of the dog matters more though. Dakota has a big, studded leather collar (rarely wears it because it wrecks his fur) and harness. Nobody thinks he's mean, probably because he's so fluffy. In fact, a lot of people thought it was funny.
I wouldn't let what other people think dictate what you put on your dog. It would be interesting though, to put him in a fluffy pink collar for a day and see how people react
I went to a couple hospitals today to see what the therapy dogs do, and one lady had her Bullmastiff wearing this ridiculously cutesy, frilly collar and carrying a rose.
Totally took the "edge" off of the huge, intimidating dog.