It's similar to the "Like" button on Facebook, I suppose. I really don't see how it could work well though, since anyone can anonymously create a Google account.
It is in testing phase to see how people can abuse it. I am sure there must be many things besides email. It will be clear soon in couple of months.
The more "Google+1" or/like the better. Maybe, sooner or later, we might see Googlepage as like Fanpage
As stated above its similar to Facebook's 'Like Button'. Its been implemented in Google to improve the determination of how to rank pages if I'm not mistaken.
Google's going to have to verify user accounts somehow to make this work; otherwise, blackhat people can register tons of accounts and +1 certain websites. Maybe Google will start doing phone verification like Craigslist?
There are people who pay others to +1 their sites. If you join freelance sites like Microworkers, you will find such jobs.
This is mostly meant to improve search results but without giving people an implicit reason to start clicking on this, you wonder how many people actually will.
Yeap like a facebook like button - I have been playing with google+ today and prefer it a lot more to facebook
It's Google+, which is still in beta, but you can join by receiving an invite. I foresee some good things in bloggers' futures with Google+: How to Use Google Plus to Promote Your Blog
I don't see how this could used to influence search rankings when its so easy to get fake likes. I just got an email today that is selling +1 likes. 1000 +1s for $599