Before today, the game with most concurrent users ever on Steam was The Elder Scrolls V: Skyrim. I remember the hype on Kotaku Australia surrounding the release of that game, so I genuinely thought that record would have held until Half Life 3! But no, the massively growing popularity of DOTA 2 has taken a life of its own. Now it appears as thought the DOTA 2 beta has become the game with most concurrent users on Steam ever.
Skyrim previously held the record during its launch month, with numbers of 287,411. Like most big launches, the numbers trailed off. What's strange about the DOTA 2 beta is its steady build upwards. The lines on the graph go in completely opposite directions, and that is super interesting. I suppose it's a completely new way of building a community around a game -- start the beta, slowly invite people to the party and make it something people slowly get excited about, as opposed to spending millions on pre-launch advertising and going for the big splash on day one.
I wonder where DOTA can go from here. The game hasn't even officially been released yet!