Facebook makes billions of dollars a year (in net profit). But is 1% negligible? Would you think "eh, that's not really that big of a deal" or would you think that's a particularly good thing? For perspective, 1% of 1 billion is 10 million, and then that 10 million would be divided up among a few charities.
Also, keep in mind they often make several billion a year, anywhere from 3 billions to 20 billion, according to my very brief Google search. So that 1% would likely be more than 10 million.