I friended Avaaz on my Facebook and get an email every now and then. You can chose to have no further communications or for me, I ticked the box on environmental issues (and a few others) so only get notified of relevant campaigns. It's so easy just giving your email address (not passed on). Just enough to let people know you care and that they are accountable.
I'm not a placard swinging type but the vast majority of people would never behave like this and those that do need to know they can't solve a problem by creating another. Thanks folks