According to PCGamesN, the ranks of total Minecrafters out there has swollen to include over 8 million players total, and that's just the PC version.
Total players on the XBLA version hit the 4 million mark (a stat no doubt helped along by the fact that the version is selling approximately 17,000 copies a day) just last month, making Minecraft one of the most played titles on both platforms.
Given such sales, Minecraft developer Mojang is set to almost double its profits this year, and is well on track to take in over $17 million this year, as opposed to last year's almost $9 million.
Since the game debuted on XBLA in early May, Minecraft has sold more than 3 million copies, and was reported as being profitable within an hour of availability, selling 400,000 in the first 24 hours. It then went on to hit 1 million sales 4 days later. Not utilizing advertising and relying mostly on word of mouth certainly haven't hurt the title. As a matter of fact, Minecraft videos make youtube's front page almost daily, helping to spread knowledge about the game, and show off some of players' more impressive builds.
An open ended sandbox (literally) style game available for less than $30, it's not hard to see why so many people have latched onto the Minecraft phenomenon, and updates to both the XBLA and PC version (like the massive Halloween update that recently went live) should help keep even more players to get involved.
The amount of registered Minecraft players is substantial at the 8 figure mark. Similar to Angry Birds, Minecraft also has a slew of merchandise including shirts, scarves, magnets, sticky pads, and recently, even Legos. Mojang, is even open to the idea of a movie or television show. It even has its very own convention called "Minecon," and was recently celebrated at Disneyland Paris.