Obviously due to the $100 price cut, but a great week for Sony all in, really. These are hardware sales as per VGChartz for last week in the States:
PS3: 41,005 (this week) 1,624,358 (total)
360: 35,084 (this week) 6,537,592 (total)
In related news, the first buses have been seen in the UK (I saw 3 or 4 this morning in Glasgow) with the PS3 Starter Pack adverts all over the sides with ‘Save over £100’ on them. Good stuff.