The numbers are by no means definitive, but the inferences to be drawn from last month’s Hitwise tracking figures have to have a lot of online marketers wondering, "What if…?"

Marketers expect users to go to search engines — and then to other sites for shopping and buying information — and Google, Yahoo! Search and MSN Search are the top three search engines for doing just that.

But in addition, Hitwise reports that the social networking site accounted for 2.53% of the upstream visits to shopping and classifieds sites for the same time period. That is up from 1.28% six months ago — and would place the site fourth on the list above if it were a search engine.

According to Hitwise, the shopping and classifieds sites that benefited the most from MySpace visits were eBay, Amazon, Gateway, Wal-Mart and Craigslist.

"Search is a proven method of acquiring traffic and Google is the leader in driving online retail site traffic," Bill Tancer of Hitwise told MediaPost. "But with the growth of MySpace and others, online retailers should expand their focus beyond search to consider social networking sites as a source of additional traffic."

That may be an idea whose time is coming, quickly.

More here.