Groupon Waits As Firms Line Up To Kill

Groupon Inc (NASDAQ:GRPN) has faced its share of problems since its initial public offering last year. Most of those problems, however, have not been external. Groupon's issues have almost all come from the inside. Now businesses are lining up to attack the tech company, hitting at its most visible vulnerability.

The idea of a sustained competitive advantage, or a moat, was popularized by Harvard Business School's Michael Porter. It involves a company having something that is not available to its competitors that allows it to compete over a long period. It involves having access to something that...