Has Google rounded down your sites PR?

I noticed recently that the PR (little green bar) has been lowered on my site. For at least 2 years it's been PR 7. The ranking for our keywords is fine, the number of visitors is fine as well.

I know that the little green bar doesn't give much information and can't be relied upon but it's just a little disconcerting.

Have Google rounded down PR's in general? After looking at a few other site I think they have. Any ideas? If Matt Cutts is reading I love an idea of what's happened.

If you've had a similar thing happen to your site let me know.