It is worth noting that both Twitter and Facebook have worked to turn their "relevancy" signals into what amounts to ad units. The signal available there basica

It is worth noting that both Twitter and Facebook have worked to turn their "relevancy" signals into what amounts to ad units. The signal available there basically represents things along the lines of either viral humor pieces, large brand ads, or both. It is further worth noting that when HP researchers looked at viral Tweets that they generally represented an echo of content from sources which were already popular and already had strong distribution channels outside of Twitter. http://h30507.www3.hp.com/t5/Data-Central/HP-research-shows-mainstream-media-drive-Twitter-trends-to-a/ba-p/87985 http://h30507.www3.hp.com/t5/Data-Central/HP-research-shows-... So rather than finding new relevancy signals, it is mostly just re-highlighting/hyping/amplifying that which is already popular. Add into the pay-to-play models where the relevancy signals are basically also sold as ad units and I am not very convinced that these aid true relevancy. Rather they might just highlight the business operations which already have plenty of relevancy signals, those doing off topic viral humor pieces, and those who have large ad budgets to blow through while trying to claim how innovative their marketing approach is. All the above said, the ability to monetize the "relevancy" signal will cause some search engines to want to lean on it, because ultimately if they can monetize the relevancy signals that allows them to monetize the organic search results as well, while claiming the results are "organic." I don't expect Google to want to put a lot of weight on Facebook likes (doing so would subsidize a directly competing ad network) but I would expect Google to put significant weight on +1 clicks at some point.