ValleyWag reported that Facebook is now providing 19% of Google's search traffic, add in 3% or so from MySpace (that could get higher if implemented better) and the fact that Twitter is fast becoming a major traffic source for many websites and you can start to see the influence that social media have on search.
Granted Google has strong relationships with most of the social media companies, but if that were to change Google could see a drop in their high percentage of market share, Wonder why Microsoft has not thought of this yet!
Optimising Digital Marketing Campaigns with Search, Social and Analytics
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