This e-mail was received on the Map Support line:
How do I remove a map from 'My Maps?
The short answer is that we've not enabled that option quite yet. Eventually that will be enabled, but for now, the only deletion options are set for deleting routes and custom places from your personal accounts.
Currently you can delete the route and markers if you so chose (by clicking on the map name in your "My Maps" search box, but the Map name will remain.
Depending upon some procedural programming work, we'll probably enable that in about a month or so.