There could be some other special velocity than c. Like, imagine there's some special reference frame in which you can send superluminal signals at exactly 2.71828 c in any direction. In other reference frames, this special velocity depends on which direction you send the signal. Lorentz invariance is broken. But the only implication for local causality is that you need to make your bubble 2.71828 times bigger.
http://www.nature.com/news/2011/110922/full/news.2011.554.html
http://arxiv.org/abs/1109.4897v1
http://usersguidetotheuniverse.com/?p=2169
http://news.ycombinator.com/item?id=3027056
Perhaps the end of the era of the light cone and beginning of the era of the neutrino cone? I'd be curious to see your probability estimates for whether this theory pans out. Or other crackpot hypotheses to explain the results.