It's not unusual to disallow coupons on the sale price of items. I admit that's questionable, but...
GroupOn didn't do this. FTD did. As far as GroupOn knew, everything was good, so far as I can tell. Throwing mud on their name without any proof at all is wrong.
I had a similar experience with FTD when using a coupon code from the "My Coke Rewards" promotion. I imagine this is their standard operating procedure.
It's the only site I've used where you can't fill up your cart and then apply a coupon code. You have to start from scratch with a special URL that apparently changes the prices as you're browsing.
...yeah, not so much. It's GroupOn's responsibility to make sure that the deals they come up with aren't being totally negated by this kind of merchant shenanigans. If they knew or if they didn't, they still screwed up here.
GroupOn didn't do this. FTD did. As far as GroupOn knew, everything was good, so far as I can tell. Throwing mud on their name without any proof at all is wrong.