Groupon in the UK has been accused of breaching consumer regulations
It's a pity our watchdog, or should we say puppy watcher, does nothing here with daily deals sites. The self regulation model doesn't work that well.
http://www.theinquirer.net/inquirer/news/2161462/uk-trade-wa…
In the US, if you do not use your voucher, the value you have paid is still valid for a few years. So if you paid %50 for a $100 value, you still have the $50 to spend if you did not use it by the deal expire date. I think that is fair to the consumer and vendor.