You see that Google+ icon either on the left hand side or the top right of this content? Well, every time you plus one vote up this content, Google tracks it. It is supposedly reported within Google Analytics, no longer Webmaster Tools.
That being said, those who track their Google+ votes have been saying the number has been dropping significantly recently.
One webmaster said in a WebmasterWorld thread:
I was just reviewing my +1's on my one of my Plus Sites. Today It went from over 6000 down to around 360 +1's. Is this happening to anyone else? First it was WMTs links to the homepage not showing up, then the removal of a screen in Index Status, now this. They are on a mad tear lately.
That seems incredibly drastic!
There are plenty of "me too" posts following that post.
There are dozens of posts in the Google+ Help forum as well with the issue. There a top contributor said:
I think it's a glitch. Similar things have happened before, and the numbers usually returned to what they should be after a while. I have pages that are affected too.
No word from Google on if this is a feature or a bug.
Forum discussion at Google+ Help & WebmasterWorld.

Comments:
Roger
02/12/2013 03:00 pm
It's only when using Google Chrome. Using Internet Explorer shows the right number of votes.
Kaloyan Banev
02/12/2013 04:19 pm
I also saw this when I was using SEOQuake a day ago. Honestly, It doesn't really matter!
Raphael DOUCET
02/12/2013 04:55 pm
Hello, do the test being and not being connected to your account, the +1 return
Raul Lazar
02/12/2013 05:08 pm
Yes, there is some bug, because i had on one of my sites 155k, really?! I verified that info with many tools because it was impossible and all of them reported the same...from 132 to155k it's a long way...:D . Now it's back to normal...
Operation Technology
02/12/2013 05:24 pm
Chrome and FireFox do not show the correct numbers. As Roger says, IE is correct. Go figure.
Ray
02/12/2013 05:59 pm
im seeing less +1 annotations in the search results. before it was everywhere and very accessible, now its becoming scarce