Understanding Impersonation in SSAS 2008

It took some time for me to understand impersonation in SSAS 2008, hope following links, would be helpful to understand it in better way:

http://social.msdn.microsoft.com/Forums/en-US/sqlanalysisservices/thread/80799351-a1d1-4c08-8b31-bb95d1053fd3/#0e002801-236c-481b-8e1a-5d40015e2020

http://social.msdn.microsoft.com/Forums/en-US/sqlanalysisservices/thread/62e56047-442e-4d6e-9aa3-a3ae6a52e206

Any further questions would be greatly appreciated.