The first couple daily deals I did, back in late '09 - early '10, I naively ran at a 50/50 split and got hammered. I break even at a 70/30 revenue split offering a 40% discount. I don't mind breaking even or even losing a bit, as I was driving more eyeballs to a site which is predicated on repeat customers. But what I learned was that the type of customers who come in using daily deal vouchers are not good customers. They'll spend the exact amount of the voucher, not a penny more not a penny less, and never return. So all it ends up is doing is driving up my labor costs to break even on customers who would never return.
After running on 15+ daily deal sites from late '09 -July '11, I haven't done another since. But boy do they harass me.