"pledges" != success
If clicking on a "pledge" is as easy as clicking on a "like", why would this be any different to the "KONY2012" campaign, or any other flash-in-the-pan click-button activision attempts? It seems almost insulting that facebook would use the same method of activism that a 12 year old would use on Facebook, despite having the power to do so much more.
Having said that, I fully expect facebook to claim success when people click on it, despite the inevitable streisand effect as people ramp up their trolling in response to it.