My cousin is majoring in Econ at Duke and is premed (he's only a sophomore). It's a great idea, also since you have a backup plan if you choose not to go to med school.
I also have a friend here that is doublemajoring in Bio and Econ. She got in to Tufts eraly acceptance.
I know another girl who double-majored in econ and bio, graduated last year and I think only chose to apply to D.O. schools.