The Google search algorithm needs Digg. Why? It provides a human feedback mechanism that can help continuously refine Google search results. If you subscribe to my blind five year old principle, social search data would be a stream of higher intelligence that will make the algorithm smarter.
Social search results would be the algorithm's tutor.
Predictions of SEO mayhem are simply unwarranted. Google knows that only a small portion of users would use the interface. And that's all it wants and needs. It simply wants to augment the algorithm for the vast majority of Google searches with a human quality assurance mechanism. In some ways, it would be a volunteer version of Mechanical Turk.
Google experimented with social search earlier this year and has been in on-again off-again negotiations with Digg. Clearly, there is a build versus buy dilemma. Google built some of the infrastructure, but might be struggling with the logic and filters to prevent gaming the system.
A black hat filter is critical since Google wouldn't want to feed the algorithm bad data. Garbage in, garbage out. But done right, social search results would help identify web spam and curtail over-optimization.
Microsoft has also been sniffing around Digg and this week launched U Rank, which is eerily similar to Google's social search experiment. Could Microsoft leapfrog Google and begin adding an intelligent data stream into their search algorithm? I find it hard to believe, but stranger things have happened.
I do believe the U Rank test will reignite Google's interest in the concept (if it ever really waned) and might again bring rumors of a Digg acquisition back to life.