While I certainly support the concept of a petition, I have a real problem with the particular site they are using to get the signatures. Before it would allow me to sign the petition the system puts up a message saying:
"Causes would like to access your public profile, friend list and email address.
Apps accessing your public profile get your name, profile picture, age range, gender, language, country and other public information."
I am not about to give out that sort of information to some group that is randomly harvesting it. I have no way of knowing how and by whom that information will be used.