Guess again: The #1 video sharing site is Yahoo Video, followed by MySpace Videos, with YouTube in the #3 spot. That’s according to numbers from MediaMetrix published by Erick Schonfeld.

Of course, with 16.1 million monthly visitors to Yahoo’s 21.1 million, YouTube is not far behind at all — and it’s got famously fast growth.

On the other hand, Yahoo has, shall we say, a bit more mature of a business model. And has anyone else noticed slowdowns and sluggishness on YouTube? If they’re really pushing 200TB/day (or perhaps the more realistic 2.4TB/day) it would not be surprising to see that they were filling up their pipes occasionally.