I think that it would be a worthwhile project for Wiki DC. Petitions at whitehouse.gove require 25,000 signatures, and it would be a mistake to start one if we are not sure that we could get at least 25,000 people to sign.
We would probably need to set up a website and a Facebook group and get
some sort of mailing list, and then once we have a large group of
interested people, push ahead with a petition and legislation drive. Or
something like that. I've set up a page on Commons to brainstorm
ideas... http://commons.wikimedia.org/wiki/Commons:Freedom_of_panorama_campaign