I did my buy my sons the occasional doll when they were little enough to show interest in them. One son was three when a cheap, "fake" Barbie-doll on a card in the store caught his eye. The doll had roller skates, a helmet, and skating equipment. Since it wasn't a "provocative-type" Barbie, and since it was cheap I let him have it.
There was also the boy-baby doll here or there, a boy Cabbage Patch doll (with adoption certificate, and one of my sons is adopted; and named, "Gaspar", although my son couldn't remember the name, "Gaspar" and started calling the doll, "Oilbar" LOL). Anyway, yes. I bought my sons dolls. Once they got a little older they were more interested in action figures and other "dolls" meant for boys.
I wouldn't have given either of them something like a ballerina or prom-dress kind of Barbie doll, and I wouldn't have given them a doll that's dressed in frilly little girls' clothes - or anything like that. If either of them had wanted that kind of doll (even as preschoolers) - I'm sorry - I would have found a different kind of doll for them. They didn't, though. Their interest (even as preschoolers) in any one doll was pretty fleeting. Doll-house people (like the Little Tykes ones) kind of filled the need to "play people" and "play family" for them. That, they really did enjoy.
My daughter had the American Girl dolls, and her older brother did find the historical reproductions of the accessories interesting. He didn't particularly want one of the dolls, but he did say, "It's too bad they don't have something like that for boys." He's always been kind of "history person", but those miniature reproductions of stuff of one era or another are also kind of just cute. So, for me, it all depends on the age of the boy, the doll, the accessories, the kind of play that's associated with kind of doll, etc.
Having said that, I think it's important not to raise boys sending messages like, "boys don't want dolls," or "dolls aren't for boys". Little boys need to go through their phase of learning to nurture and processing how things like social skills in the family work. They often do things like make their sisters' Barbie doll race her sports car, so how they play with dolls is often different than the way some girls do.
For the most part, even girls stop playing with dolls (unless they just collect them) at adolescence, so if I had a close-to-adolescence boy who wanted a doll - no. :) Younger than that - I'm flexible. :)