Even Amazon allows a 30-minute cancellation on one-click orders.
I've hardly used it, but it does exist, and it's kind of scammy for LivingSocial to not have this kind of feature, even if it's limited to 15 minutes or less.
They let me cancel the trip so there is no issue with LivingSocial having that as a part of their flow, but it would be nice to have a confirmation page between purchases over a certain amount.