Letterbombing is a subversive way to deliver a message anywhere on Facebook.

You and your friends simultaneously leave posts on someone’s Facebook wall. Once you “reserve” a block of posts, change your profile pictures to a letter, spelling out anything you want.

Originally a concept for a client over at BBDO by Jeff Greenspan, Chris Baker and Danny Adrain, but the client didn’t buy it, so they decided to do it themselves.  Good on them.