Google Webmaster tools is now showing the results of your +1 activity – just click on “+1 Metrics” in your left menu in WMT.
Below is a screen shot created by Search Engine Round table – which I have used instead of my own screenshot because it had pretend stats in there making it pretty, and I didn’t have time to do that just yet.
I think the particularly interesting thing here is the ability to see whether Google +1 has had an impact on your Click through rate (comparing it to other pages though, rather than history). Apparently this information will only be shown for organic results, and only when a statistically significant change can be seen.
Under the Activity section, you can see the +1 activity over time, as a line graph. This will also show the source of your plus 1’s, which will be useful to help you grow the channel.
And the final option is to see audience, which will show aggregate demographic and audience information – not users, even if they are public. This information will only show up after there is a significant number of users +1-ing you, to protect people’s privacy.
With the introduction of Google +, +1 will likely start to be more commonly used, making this data worth looking into. People can +1 you in the search results, but to make it easier, and more logical, for people to +1 you, you might want to consider getting the badge onto your site.