From the +Mashable article:
The bottom line is, the SEO effects of a +1 are very indirect, which means traditional SEO practices should not be ignored. SEO methods such as link building, relevant keywords, and URL structure have a more significant impact on page ranking.
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How Google's +1 Button Affects SEO
Google's +1 button doesn't share content to the stream the way the Facebook "Like" does, but there must be a connection to search. Here's what we know so far.
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I think +1's are an addition to SEO… as they say 'every little helps' so it all adds up!
On that very subject, I re-shared a post from PlusRank that explains that it’s WHO +1s you, not HOW many.
https://plus.google.com/u/0/102482951505328809974/posts/aN8abkyHPaw
+Loki Wijnen Thanks for the mention, seems +Pete Cashmore came to the party a bit late, oddly enough….
https://plus.google.com/107656088609554509650/posts/U1p9jjKbsRX
We already had ours party this morning.