Yeah I see a lot of smurf's around lately too.
Fact of the matter is, unless it's within their very first calibration period they are technically on the same hidden MMR as you.
What is more irritating though, and this happens because I often 4-5 stack, is the "Stack-Smurfs".
Basically it's 5 people that can seriously play, one guy goes and makes a new account and stacks with his 4 friends. The average party hidden MMR is then 30% down, so they then face people way lower than them.
This happened to us a few times. The one game, the guy predicted, and had a 16 game correct prediction streak. They destroyed us 78- 4 or something stupid, and we not complete noobs.
You could normally recognize them by seeing 4 players of 100+ Dota level ( I know it means nothing) and the 5th maybe a 2-3.
I really don't see the point of smurfing. For me it's a reflection of weakness because you can't hack it with your peers and then have to pick on newer players.