Despite the fact that the majority of HN readers already know about SOPA, I think it's an excellent idea for these other reasons.
It might also be an opportunity to get some of us off our butts and use the time we spend reading HN each day to call our representatives in congress instead.
So you think that HN being off for a few hours will make headlines in the worlds newspapers and on the main TV channels? Maybe as an "some tech websites were also offline [and nothing important was lost]" or maybe even (given the quality of some press) "other illegal hacking sites were down in protest against the bill".
I don't have a representative in congress but nonetheless expect congress is already pushing a similar law for my country.
I find the idea lacks any force as a demonstration.
Reddit, HackerNews & SlashDot down = Tech sites blackout
Reddit down = Remember that website that we reported was full of pedophiles last month? ...