Maybe it's due to the slumping sales of Xbox Live Arcade games that game developers have been complaining about. Or maybe we can call it Gamerscore inflation. Or is Microsoft just being generous?
Whatever the case, XBLA games will be able to offer 400 Gamerscore points instead of 200, starting in April and will be required to do so by June. They'll now max out at 30 Achievements, according to Microsoft's Major Nelson.
Xbox LIVE Arcade Gamerscore Policy Change [Major Nelson blog]