After the new Maps update I noticed that just navigating back to the home screen would not turn off GPS, and I would sometimes have to use TasKiller to kill Maps completely.
Now I noticed that GPS was on even though Maps was completely shut down. I realized that just navigating to the Google Buzz mobile site (which uses GPS to determine your location) leaves the GPS running even after you close the browser.
You have to either navigate away from the site, close the tab, or kill the browser completely. If you forget to do this, your phone might be dead the next time you need it.
I'm using xScope as my browser. (I tried to confirm this with the stock browser as well, but every time I try to navigate to buzz.google.com, it opens it in xScope instead.)
So I don't know if this is a xScope issue or a Droid issue in general, but it's bad.