At least some people in the space community seem to have a sense of humor about this: the Mars Society has renamed its analog Mars research station after Colbert for a week. ;-)

The main issue is the intent of the network doing the distribution. Grokster et al were found to be illegal because they promoted lawbreaking as their primary raison d'etre -- with ads like "download the top 40 here" and other things that clearly were designed to incude infringement. Since Bittorent is content-neutral as a technology, it can't be declared illegal under MGM v. Grokster, since those who created/maintain it don't intend for its primary purposes to be infringing, and aren't encouraging infringement directly.

Go read the opinion -- it's publicly available for free, and it's really not hard to understand at all. (BTW, I copied that link straight from www.supremecourtus.gov, so it's as legit as it gets, despite what Slashdot may say about the domain. :-P)