In a
Gamasutra article discussing the use of Achievements in video games, Microsoft's Aaron Greenberg let it be known that, to date, gamers on the Xbox 360 have unlocked 2.5 billion Achievements, nearly 150 Achievements for every Live subscriber. Furthermore, 360 gamers have accumulated a gamerscore of 54 billion points. Said Greenberg, "We never anticipated this reaction... where there are Achievement fan sites and people playing games that they would never play."
_______________
Source: Joystiq