Speaking at Rezzed, Day Z's Dean Hall said: "We've got 420,000 now. We'll have 430,000 tomorrow." The Arma 3 developer reckons that his mod will end up selling more copies than Arma 2 did originally. "Currently we're running 22,000 concurrent at full peak, and 10,000 off peak, which is pretty huge numbers considering the original data structure and system was designed to handle 100 concurrents, and two servers... We now have 1000 servers. We're getting 110,000 players in a 24 hour period at the moment."
Game of the year so far, for me at least. And for a few other people, it seems. [I missed Rocket's session, sadly, so thanks to Eurogamer for covering it.]