I have a similar problem, except with the right lens. The crack looks like a stress fracture, not foreign object damage. There is no impact point. Maybe vandals are using rubber mallets nowadays. I will probably bring it up with the dealer soon (only 2 months left on the warranty). I've autocrossed it twice, but that shouldn't cause this kind of breakage. As Ron mentioned, maybe our taillight assemblies were installed prestressed. I'll post a picture tomorrow.