If ever proof was needed of the strength of PC gaming circa 2012, and in particular the appeal of Valve's Steam service, look no further than this: over the weekend, over six million people were playing PC games on Steam.
Sure, there's a big sale on, so people are buying games like there's no tomorrow, but there's also no single MASSIVE title like there was last year (see: Skyrim). Instead, as you can see, after DOTA 2 - a game that's not even technically out yet - the list is pretty unremarkable.
It was only in January that Steam hit a then-high of five million concurrent users. To hit six within the same year shows just how popular the service is getting.
UPDATE - As some have rightly pointed out, the count records how many people are logged into Steam. While you'd think many/most would have played at some point over the weekend, it's impossible to know how many were actually playing and how many were just logged in because their system preferences boot Steam on start-up.
Steam & Game Stats [Steam]