I've been using Groupon for a while and have gotten used to fast, responsive customer service for my "group coupon" deals. They even refund your money if you have problems with a deal! The other day I tried LivingSocial for a couple deals that were quite enticing, one of which was a Zoobooks deal. When I got the Zoobooks voucher and followed the directions to use it, it didn't work. I contacted LivingSocial and was told that "these types of problems are usually best answered by the merchant directly." I know that if I had a similar problem with Groupon, they would have been right on it--it's doubtful that I would have been the only person who had that problem. And apparently I wasn't, since later that day LivingSocial sent out new vouchers (the original voucher numbers were no good).
So, this doesn't bode well for their customer service. After that and after reading some of the other reviews here, I will be hesitant to use them again.