One of the most jarring comments from the above post is that these new sidewikis (essentially, a commenting page for every page on the web) actually create SERPs of their own…and could theoretically outrank the site upon which they are based!

From a reputation management perspective, anything that you do not own/control is something that must be understood and monitored. Add these sidewikis to the list. We will be investigating this more fully in the weeks and months ahead.

His ultimate conclusions are very similar to what we've found: social media (i.e. digg, reddit, stumbleupon, etc.) certainly has its positives, and you want to have a presence, but it requires a lot of work to really drive consistent, significant traffic. Search engines, on the other hand, tend to drive visitors that interact more with your site and that spend more time with your content. It obviously requires a lot of effort to ensure that your site has good SEO fundamentals, but often this effort has a greater ROI than the time investment for social media.

You can't forget about either, but the article suggests the path we typically follow: more time, focus on SEO.

http://www.smashapps.org/2009/06/search-engine-traffic-vs-social-media.html