I've been a user of Groupon deals for years. Even though Groupon has not made the money early backers predicted -- and there some problems with its business model, as evidenced by Wall Street's lack of enthusiam -- they can be a pretty good buy for consumers.

If you don't know how Groupon works, a merchant agrees to offer a product or service for a deep discount, which Groupon posts online and sends out to subscribers to its emails and smartphone applications. Typically, the number of such deals is limited, reducing exposure for the merchant. Groupon takes a substantial cut of the deal's price, so sellers have to decide if it's worthwhile.

But I've bought everything from restaurant meals to headphones through the site, and the deals keep coming, so it must work for some companies. 

This morning I received a deal alert for 80 percent off a furnace tuneup from an HVAC construction contractor. The final price is quote low: $49. What do you think of such offers? Do they devalue the servcies of other HVAC market companies? Or is it worthwhile to position a tuneup as a loss leader? 

And have you ever used a social media site such as Groupon or Living Social to boost business? Did it work?