Turns out people like Angry Birds -- and free things. The freemium Android release of Rovio Mobile's wing-slinging hit has been downloaded over 30 million times, according to Rovio's Peter Vesterbacka, who is speaking at GDC as part of a Google-run Android monetization panel.

He also provided evidence that people continue playing Angry Birds after that initial download. 80 percent of Android users, Vesterbacka said, downloaded subsequent updates, indicating that they've retained interest in the game. This is good news for Rovio, but bad news for those birds -- sustained anger isn't good for you.