Group Deals sites

What are your thoughts on all the hundreds of deals sites that are popping up? They are pretty awesome for the consumer, I've personally bought quite a few hair dressing deals and dinner vouchers.

But are they worth it for the business? Firstly - if you buy a deal for $40, the group buying site usually takes 50% from the business, so the business only receives $20 of the $40 deal. They are already selling the deal at well below half price and possibly making a loss on the deal. But the *HOPE* is there that they will get repeat business if you *TRY* their goods or services.

In my experience, I went to the few hair dressers where I bought the deals, but I haven't gone back. Why would I want to go back and pay full price? $150 full price versus $49 that I paid for the deal. I can just buy another deal for another hair dresser. Sure, if you find your most awesome hair dresser to go to regularly I understand it's worth every penny to go back there, but with the deals, it's not often the case.

Are there any businesses out there that have had good or bad experiences with using group deal/buying sites? I'd love to hear from you or your opinion on this topic! :)