The site ownership verification in Google Webmaster Tools can be an erksome item for some people. When managing a large number on Google Webmaster Tools accounts it seems that someone, somewhere is always removing the HTML or Meta tag verification information. Whether it is because they do not know what it does or because it gets left out of the next release of the code base. Anyways… Google now offers a history of their checks on the site owner verification.
The site owner verification history is a great idea!
You can now see exactly when verification fell off as Google tells you when it checked the file and it either passes or fails.
Additionally, they time stamp the date when you ownership was delegated to your account if you are not the original owner.
Just some more tidbits that Google WMTs gives you to make your day a little less painful. Enjoy!