Comic Book Resources recently interviewed the recently re-designated co-writer of Justice League of America's Vibe, Andrew Kreisberg. Here's the link for that story.
The crux of the interview, however, is this:
Detroit, which is where Darkseid's invasion started in Geoff and Jim's Justice League book, is now unstable. Pockets of the membrane of reality have been so badly damaged there that things are constantly falling through from other dimensions. And Vibe is there to help clean up the mess. Even he says that is kind of ironic being Hispanic that he has become a dimensional border patrolman.