I see hundreds of thousands of billable hours of mechanical turk and dungeon grade Indian and Chinese IT Services time spent +1ing SEO spam farm links.
As PageRank is a trust metric, and their entire system is based around that, I'd imagine they would perform similar calculations for +1 results. Especially as +1s contain no implicit content, as they are merely flags, I find it unlikely to suffer from SEO like search does - trust metrics are practically designed to handle farming.
How can you calculate a trust rank of +1s? Remember that people don't +1 other people, and don't know who +1ed what, so not even people can assess who does quality voting.
Google's aiming for the social game, and has been hosting, indexing, and correlating it for a long time. They have blogger, buzz, gmail, people's names, credit cards, links to and searching of your twitter account, your blog, your friends, your x, your y, even your z. Why can't they infer popularity that way, identically to how PageRank works?
And people do see who +1d something, it requires a public account - it's visible on the link (as displayed in the video, and implied by the same behavior with tweeted links) and on your profile page.
If a nobody from nowhere +1s a link, their friends will see it, but it's unlikely to affect the world at-large. Similarly, trust-metric wise, if a cluster of nobodies +1s a thousand pages, the impact will be restricted to their cluster. If an extremely-highly-connected person, who many people follow on Twitter / Reader / etc, +1s something, it'll have more impact simply by being visible to more people and because their "importance" can be inferred by those connections.
Agree, though reputation rank may mitigate some of this behavior when implemented. The urls +1 profile distribution may end up looking like a typical back link profile and something most SEOs should try and balance.
