If you are running 1.2.0, ads will not be taken down properly when they reach their expiration date, and you will recieve an endless supply of email notifications stating that the ad has been taken down. For every time someone loads a page on your blog, an email notification will be sent. This could quickly fill your inbox, and put unnecessary strain on the server.
This issue was caused by a mistake in an SQL statement that has since been fixed. Please update to version 1.2.1 of the WP125 ad management plugin, via the automatic updater in WordPress, or by downloading it manually.
EDIT: It seems we are up to 1.2.2 now. A couple of other, less major, bugs came up, and have since been fixed.