I don't mind when students do it--I've been there and know that it can be a pain to recruit people for research. Also, kudos to them for seeking out people in their target demo rather than using a convenient sample of their friends.

It bothers me a little more when someone is trying to do market research on the cheap for their business. Sorry, but if you want people's time, bite the bullet and compensate them, the way other companies do. It doesn't have to be much.