I think the real purpose of these blackouts is to get users to finally do something. As much as I oppose sopa/pipa it wasn't until the Wikipedia blackout with direct links to my congressman/senators contact forms that I actually took the time to write letters to all of them. It had been on my "yea yea I'll get to it" list for a long time.

Now I'm sure there are many HNers who are deeply cynical about the value of writing to senators, but honestly you have to at least give it a shot.