New Web sites provide discounts to buyers who join in social networks - Washington Business Journal:

Buying online. Buying with PayPal. Buying on eBay. It’s a list that seems never ending in the digital world, and now there is a new buying trend hitting the hospitality and retail industries — group buying.

No fewer than four companies, two of them locally based, have come on the scene in recent months offering discounts on everything from restaurant visits to spa treatments...