Yahoo has been the longtime leader on the Web so, naturally, these results were immediately called into question. UBS analyst Ben Schachter later warned reporters and investors that this is potentially unreliable data. Nielsen/NetRatings' data still has Yahoo on top, with 33.4 billion versus FIM's 29.

This debate might strike advertisers as a little ridiculous. Sure, Yahoo's growth has slowed considerably, while MySpace's has surged. But no one that buys media would consider FIM's largely MySpace-driven traffic more valuable than Yahoo's.

Yahoo's pages are closely monitored, and the vast majority of them PC and child-safe, while enjoying tremendous usage. MySpace's growth, while closely monitored by the ad industry, is still largely unusable; user-generated content can't guarantee the PG-13 rating needed to make it ad-safe.

The debate here is really between competing research firms. None of the panel-based data crunchers have completely accurate data. Everyone knows this, though they're working harder to fix the problem.

Read the whole story at Business Week.

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