The Word of Notch offers a poll, as Mojang wants to be sure Minecraft players are okay with them collecting data before they attempt to learn more about how their game is played:
Right now, the only way we can figure out roughly what people are doing with the game is to track logins. Once you’re logged in, we have no idea what happens.
I was thinking it would be awesomely cool to add some kind of player tracking to the game. This would work by having the game connect to minecraft.net and send some anonymous and non-private data about the game, such as current game mode (single player, multiplayer), operating system (windows? mac?), how long you’ve been playing for (so we know how long a game session is), and whether or not you’re playing the downloaded game, or the applet on the webpage. It would probably connect every ten minutes or so so we can get some semi-realtime data. We’d share the data with the community, as usual.
Naturally, the data sent will be fully anonymous, so it wouldn’t contain any session information or your user name, and it wouldn’t send any sensitive information that you might not want to share.
Would you be ok with this? We’d really appreciate having that data!