Its a great read, and I highly recommend you read it too. You can find it here.
Here's a couple things that really got my attention:
Each cause had at least one personal 'champion' who leveraged their networks and friends and worked many many hours to activate them.
"... cause champions [people who participated in the Facebook 'Causes' contest] found that impersonal group emails were completely ineffective."
"A mix of activities was evident in all of the successful efforts that included Internet, mobile-based activities, and in person solicitations."
It's not just about the money! "Yes, we're thankful we won the money. But the exposure for our organization was priceless."
Just my two cents from the sidelines, but I think a big part of the 'secret sauce' is the passion and motivation of each of the people who worked on the campaigns. Their personal belief and willingness to talk about it and express it to everyone provides the fuel for the engine.