User blog comment:DaNASCAT/Technical Update: June 5, 2012/@comment-100066-20120605180134/@comment-1656630-20120605192039

We recently added support for sitewide messages to anonymous users, and the bubble's placement interfered with the toolbar that anons see. We picked a new location that could be consistent for all user states.

Personally, I'm finding it pleasantly less invasive. If I have a notification I wasn't ready to click on yet, it no longer gets in the way of my content reading. But it will be interesting to see how it feels after another week.