See the netcast from the 2011 Fall Member Meeting session titled
"Where the Sidewalk Used to End--Privilege and Policy Management Strategies" with speakers from Clemson and U. Penn
http://events.internet2.edu/2011/fall-mm/agenda.cfm?go=session&id=10002005&event=1148
Chris Hyzer's slides are at : http://www.internet2.edu/presentations/fall11/20111004-hyzer-sidwalkends.pdf