On the other hand, I did some research assistant work for my prof one summer, and he put my name on the paper the came out of it (as second author). But I didn't even understand half of what the paper said! I was a first year undergrad, and he was presumably hoping to help me "build a resume" and "get my name out there". It's an awesome gesture, and I think it happens a lot.

Furthermore, "Einstein and Noname grad student's method for solving X" sounds a lot better than "Noname's method for X". People will read it more and it will disseminate faster. The student will ultimately be better off.