A New Dot-Com Bubble? Frothy Valuations for Facebook and Groupon are Sparking Worries

With valuations of Web-based companies like Facebook Inc. and Groupon Inc. zooming ever higher, questions have been raised over what these companies are truly worth and whether we're seeing the early stages of a new dot-com bubble. "The markets are showing signs of speculative froth," Martin Sorrell, chief executive officer of marketing giant WPP PLC (Nasdaq ADR: WPPGY), told the trade journal Information Age in a recent interview. And the social media companies seem to be whipping up the bulk of that froth.