In relation to WHH, I've been thinking about the scene where Jack, as a Dharma janitor, is cleaning the classroom and attempts to erase what appears to be a history lesson from the blackboard. This is likely forshadowing of him attempting to erase the history of Oceanic Flight 815 from the island by dropping the bomb, but he didn't quite wipe the slate clean. Although not as vivid, the words are still legible which leads me to believe his scheme was not completely successful, but nonetheless, history has been altered in some way.
Of course it's possible this may have just been the writers setting us up for the fact that some of the show's history will be figuratively wiped away, like Olivia, Annie, and the volcano. Or maybe it's both. Stuff like this drives me crazy trying to figure it out, but at the same time I'm giddy with delight in the discovery of a possible clue. Thoughts? Please!