slartythefirst - 10:53 am on Sep 30, 2010 (gmt 0)

As mentioned already, SMM may already be more effective than SEO, for some sites. That could be dangerous for those sites if they put all their effort into SMM and neglect SEO.

With SEO, by now, we all understand it's about the content; Good content that people want to link to.

SMM is about grabbing what traffic you can, while it's still available.

SEO is not restricted by product or target age group.
SMM is more about current topics of interest to a younger demographic.

Search Engines, or at least the ability to search the web for information, will be around for as long as the web will.

Social Networks are subject to massive change and upheaval - they're an unstable source of traffic.

Does anyone remember Bebo or MySpace?

I'd say, stick with SEO and put an approriate amount of time into SMM. Grab it while it's there.