well i think they have to get some amt of data first... obviously they'll add this to the algorithm and let the machine learning decide how much to weight it. I think it will likely increase click throughs by a decent multiple (for the most +1'ed results). I actually did a proof of concept on organizing search results by facebook like counts last year http://news.ycombinator.com/item?id=1372311 (and oddly enough i did see a spike in mountain view traffic this past december :).