Techcrunch: Scrabulous Gets Wiped Off Facebook:

Long outplayed by two Indian brothers, Hasbro finally delivers a massive counter blow to Scrabulous, one of the most loved games on Facebook. Scrabulous fans in North America will see the following message when they try to play the game:
Scrabulous is disabled for U.S. and Canadian users until further notice. If you would like to stay informed about developments in this matter, please click here.

Coverage from Alley Insider here.
UPDATE: NY Times reports that Scrabulous requested that Facebook disable Scrabulous for US and Canada