Yes, that is one hundred million games of Dota 2, thanks to a monthly player base the size of a small country (like, oh, I don't know, Lithuania).
Those stats come from a casual postscript in the Dota team's blog, as part of an update on the new Least Played mode and improvements to the Shared Content panel. If you still weren't sure whether Dota 2 was taking off, this should make it all clear. "The Dota 2 community is blossoming into a beautiful flower," the blog post says.
Don't forget, that's one hundred million games of something that's still in closed beta, a game that hasn't been officially released yet. That said, there are so many gift copies of Dota floating around that you'd probably have a tougher time breaking into a paper bag. I'm still struggling to give mine away.
Three million players, eh? With up to ten people per game, that's an awful lot of people trying to solo mid. There's got to be a few easy targets out there.