I wouldn't say they're exploiting a loophole in the human psyche, rather a very well known aspect of it.

It's also a brilliant business model for a recession and financial crisis. In most instances it's win-win-win:

- Groupon makes money

- people get huge discounts, and save money if it was something they were planing to buy anyway.

- businesses both make money (assuming they worked out the math of the deal correctly before accepting it) and gain huge exposure.

I suppose the only losers are wherever people would have spent that money had they not bought the groupon, but that's hard to quantify (bought the same thing at a higher price? bought something else? saved it?).

I can't think of many more innovative business models for a distressed economy.