The game of Risk (also a Hasbro property) has a multitude of imitations around the web, one of which is my web-based version, called Grand Strategy (www.denizengames.com). I've heard from the creators of other Risk games that they have been threatened by Hasbro if they have used Risk trademarks. I believe that the precedent is fairly clear: Hasbro and other corporate entities won't touch you if you stay away from trademarks, game rules cannot be copyrighted.
What's amazing is how poorly done Scrabulous is. The site design, flow and presentation are incredibly weak. A fair amount of the site appears to be "under construction". And they're going to pay tens of millions for that?