I think doing what you are hired for or what you are good at might only work at bigger corporates. A mid size company (150 FTEs) like mine where the IT team is only 7 people, you are everything from the tech support specialist to the DBA trying to maintain a HA environment for the data warehouse!!

In fact, I think our HR gets away with it too because there is a clause in our contracts that reads "other duties as and when required". And moreover, in these economic times where everyone is worried about their job security, I don't even mind clearing a paper jam in the printer or trying to get the CEO's BB to synch up with her Outlook!!

That being said, in an ideal world though it would make perfect sense for any staff to do what he/she is best trained and hired for and the various managers/bosses should have some faith in their subordinates and let them take charge of performing and fulfilling their duties.