I'd sign it probably if there was actually any content showing for the petition. Not sure if it is just me but no petition text is listed.
I've never had any confirmation that online petitions are even seen by the people the petition is for or if it had any effect one way or another.
This site actually sends an email to whoever is being petitioned on behalf of each person that signs. You can see the content of the email under one of the tabs on page. Another tab states the purpose of the petition as defined by its creator.
Ah must just be my browser or something as none of the tabs contain anything but an email link for me.
Petitions may not make much difference overall but any little good they do is worth my time.