A Facebook or Twitter (or similar online media) user who invests a huge 5-minute effort into saving the world via link-sharing and hardcore online chat.
Much like the keyboard warrior, the keyboard philanthropist has no genuine intentions whatsoever (though he/she may become overtly aggressive or enthusiastic if engaged), and is always best approached with a healthy amount of sarcasm, a Neil deGrasse Tyson Reaction meme or a taser.
Person 1: OMG guys that Kony guy is such a dickweed!!! Help me save Uganda by clicking 'like' or 'share' =)!
Person 2: Watch out Kony, you're dealing with a keyboard philanthropist over here...