In the grand scheme of things, it doesn't really matter which race is used most, as they're all quite well balanced (and getting better with time).
If I had to guess, it's something along the lines of Toss >= Terran > Zerg. I recall hearing that Toss is the most popular a while ago, but this may have changed since and Terran is just so easy to play, I'm unsure of their standing. Also, there are tons of players who try Zerg, but fail miserably and quit, or fail miserably and keep trying (but continue to fail). Lol.
The philosopher, you know so much about nothing at all.