Looking at the database, it appears that calling the removeUser() method doesn't cleanup all other user related information in the JBoss portal database.
I see user references left in jbp_instance_per_user. Don't know what else might be lingering.
Is there some other method of removing inactive users?
Found part of the solution, by using the following method:
But now I'm wondering how one removes portlet preferences that are not associated with dashboard portlets. How does one find the portlets that a user has customized via the API?