With Social Search, we improve your results by relying on the context of your friends, family, coworkers and other people you may care about across the web. We’ll sometimes improve the ranking of results if they’re more likely to be relevant based on your social connections. We’ll also highlight your connections by showing their names and pictures in the results when they’ve published or commented on content, for example by clicking the +1 button.
Interesting – this new post by Google Fellow Amit Singhal confirms that sites/posts your friends like will be boosted within the Google Search results.
It’s an indirect social signal and benefit of encouraging social sharing of content on your blog. It’s also another reason to use the great new “Verbatim” feature to manually check rankings.