I know that in DotA, making a smurf is like a death sentence. I think Valve has pretty powerful smurf detection software since they can already tell when somebody is making multiple Steam accounts from the same address. It's in their best interest to track that sort of thing. If they catch you making a DotA smurf using that method, you are punished HEAVILY. I mean, pitted against people who have played 3,000+ games heavily.
At one point, I made a smurf to play with my ex-girlfriend because she was really new to the game and I felt that pitting her against people at my level would be disastrous, but the people we got using my smurf to queue were probably even out of my skill league, and I've been playing for over 10 years, if that tells you anything.