I was just wondering why the 29th Century Federation didn't intervene with what happened with the Narada going back in time and creating a whole new timeline. The USS Relativity was established as a time ship whose purpose was "to protect the timeline against temporal incursions." I'm pretty sure Nero going back and blowing up a planet and possibly Earth counts as a temporal incursion. I'm not taking this too seriously but it's just a thought that occurred to me one day on my couch.