Google will start to look at +1′s as one of the many signals we use to determine a page’s relevance and ranking, including social signals from other services. For +1′s, as with any new ranking signal, we’ll be starting carefully and learning how those signals affect search quality over time.
Content recommended by friends and acquaintances is often more relevant than content from strangers. For example, a movie review from an expert is useful, but a movie review from a friend who shares your tastes can be even better. Because of this, +1’s from friends and contacts can be a useful signal to Google when determining the relevance of your page to a user’s query.
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