Sorry if this has been posted before, but I'm always signing petitions on Change.org and was cynically wondering what happens to the 'donations' they ask for to get the petition "on the agenda".
It doesn't look like it goes directly towards whatever campaign you are supporting but to Change themselves, and they appear to be able to do what they want with it:
twocents.lifehacker.com/before-you-chip-in-on-change-org-read-this-1843998045
The article encourages you to be aware of where your money may be going before you donate.