Read more about the subjet here: http://www.techspot.com/news/43064-google-adds-1-button-to-search-results.html
Beside being something that will be definitely abused by spammers and SEOs, don't you think it's very unfair for small business?
For a company with many employees it will be very easy to force them to add a +1 each, thus resulting in company's website being upvoted a number of times that is directly proportional to the number of employees the company have.
I know you might say: "well also in real life is like this, if you have many employees, they will spread the voice about your company", but I think it's different, because I heard many times employees talking bad about the company where they work, but they won't be able to do the same on Google cause the manager would immediately track who did not upvote the company website, and as far as I know you can not downvote (I mean they can not even create a fake profile to just downvote, but let's not get into this right now).
UPDATE: After reading some answer I thought to make clear that I did not talk about ranking in this question, probably adding the word
SEO at the beginning of the title was somehow misleading.
I do not think this new +1 feaure could influence ranking (at least for now), but still it will definitely influence clicks on results in SERPs, we'll probably see also a new type of SEO.