Alternatively a different auth module could read and extra field that point the user to a different root directory.
sjorge ==> /server/host/www.blackdot.be wrowe ==> /server/host/apache.org ... this way the user name would be free of @'s :) Downside would be: 1. multiple domains can't have the same user account 2. a new auth module/provider (2.2.X has me confused on the split up auth module system) so that and extra field is stored that holds the domain name which will point it to the correct vhost. Maybe the comment field can be used for storing this?