I agree, though other petitions can be effective. If you care about a cause, place your signature on a petition hosted with an organization that will tirelessly advocate for that cause. Organizations in turn live and die by their ability to gather and show support for the causes they fight.
If there's anything techies should've learned from the SOPA battle, it's that it is possible to make political change when enough people speak out. If you haven't watched aaronsw's talk on stopping SOPA, it's well worth your time. https://www.youtube.com/watch?v=Fgh2dFngFsg