DOTA takes Steam concurrent player record... from itself
At some point this past weekend, there were 329,977 Steam users running DOTA 2. That's a new record for any single game on the Steam platform, beating down the previous record of ~297,000 players gathered in DOTA 2 in early March. The West qualifiers for The International tournament -- with a prize pool currently topping $2 million -- were this weekend, and folks can watch through the client, so that probably had something to do with it.
Thanks, PC Gamer