Groupon Inc., the No. 1 online deals service, failed to show investors its business is growing as quickly as they would like, as it was hurt by what it called "continued challenges" from the economic weakness in Europe. The company booked a small loss in the third quarter as higher revenue wasn't enough to make up for stock compensation and other expenses. Its stock fell sharply in after-hours trading, indicating it will likely open at its lowest level ever when regular trading starts today.
