Groupon allows many crooks and unreputable vendors on their website. I've had problems with Groupon in the past and I wouldn't recommend it to anyone. Occasionally a purchase will go fine, but overall it's a very risky website.

EDITING DUE TO THE (FALSE) REPLY FROM GROUPON.....
Don't waste your time trying to work through things with this customer service that they refer to. It is a joke. Groupon ruined my Christmas trip to NYC.
Here are some examples of how their customer service "assisted" me. (NOT!!)
One of the purchases for a restaurant didn't come through for me to use at check out, so we ended up being out of pocket of Fortune since we weren't able to apply the Groupon! I assumed the Groupon was in my wallet when we ordered from the menu. I paid for that Groupon, and Groupon did not deliver.... But they sure were proficient when it came to charging my credit card! Double whammy!
In addition, I tried to explain to them that purchases were made on my account that I didn't make. They were made on the day that I left NYC! Trying to get Groupon to understand what had transpired was a waste of time. I had several different customer support agents contacting me, and none of them helped me. I had to end up disputing the charges with my credit card company. It was a nightmare! I'll say it again....BUYERS BEWARE!!