I used Living Social for some small things like restaurant coupons with no problem. But I took a risk and bought a Book-A-Tailor coupon so my husband could get a tailor-made suit. 6 months and 3 suits later, he still doesn't have a suit he can wear and Living Social says once the coupon is redeemed, they will not get involved.
I also had a bad experience with carpet cleaners. I don't think they screen their offers so beware, you are on your own. I've had much better luck using Groupons.