More annoying (but more visible) idea:

Everyone changes their name to "SOPA Enforcement Officer #204295" with an official looking picture, and combs through their friends posts all day looking for pictures or text that would potentially be taken down under a nightmare SOPA regime.

T-shirts or products with logos visible, artwork visible, song lyrics, videos with uncleared background music. Get creative.

Then, post fake takedown notices (in the comments) with an informational link.