I'm using Jetpack 2.0 on WordPress 3.4.2 and the Carousel is behaving badly.
If you look at this page you will see the gallery. Clicking any image opens the full-screen carousel. Navigating between images works properly. Closing the carousel works properly.
What does NOT work properly is the browser's "back" button.
After browsing several images using the Carousel, then closing it and trying to use the browser's back button, you will see the URL change to show each anchor visited in the carousel. For instance, if I view three images in the carousel, then close it and hit the back button, I have to hit it five times before I actually go BACK to the actual page I came from:
I've seen the same behavior on other sites running the carousel, such as http://kovshenin.com/2012/jetpack-carousel/
This seems like a bug, to me.