DOMA Dead? Dun Dun DUNNN!!

So Obama has decided not to defend constitutional challenges to the Defence of Marriage Act. What practical difference will this make? One reason DOMA was passed was to prevent same-sex married couples from being able to demand that their marriages from being recognized in states that don't want to recognize them. Will people be able to do this now? Will people be able to cite the full faith and credit clause to force states to recognize same sex marriages performed in other states? Will the SCOTUS uphold its constitutionality without the Attorney General defending it?