Amicus Briefs in MGM v. Grokster

If you haven’t checked it out, 28 amici briefs have been filed so far in the MGM v. Grokster case, including three different briefs led by law professors. I find it particularly interesting that Sen. Leahy and Hatch submitted a brief. It seems like they can influence the outcome in a lot of ways, so why did they need to resort to an amicus brief? I would expect a healthy number of briefs supporting Grokster on March 1. What will the court do with this deluge of submissions?