Though it is early with respect to Google+ and +1, noting the impact Google has on the internet universe, it doesn't really make sense to not incorporate a Plus strategy into your social media efforts...
Author Rank is where the internet is implicitly headed. If Panda weeded out low-quality content, and Penguin decimated low-ball link graphs, the next logical move will be to go after the million and one FAKE USERS, accounts, and spammed content that are created daily with automation.
It's time to GET REAL with Google+ if you aren't already, cuz this is one fence you don't want to be sitting on the wrong side of.
Consider the following scenario.
- Document 1, Domain Name A, Content X, Author=John Smith
- Document 2, Domain Name B, Content X, Author=John Smith
- Document 3, Domain Name C, Content Y, Author=John Smith
- Document 4, Domain Name D, Content Z, Author=John Smith
How many different Authors are here involved?
Which John Smith is claiming which document(s)?
The rel=author is a two way street. You can claim authorship on site if you control the site or no one there checks ownership before giving it to you. That site links to your google+ profile.
Part 2 requires that you link to the original content from your google+ page creating a reciprocal link. The odds of being able to fake both ends of the handshake are minimal and are generally considered to be safe from tampering at this point. (barring actual site hacking).
There can be an infinite number of John Smith's because they will each link back to their own unique G+ page. It's not that hard.