Department of State Foreign Service Officers (FSOs) are probably the best example of Gov't up or out. They really do let go of low performers.
I view our gov't workforce as: 1) Mission - people that actually do the work. So think lawyers, doctors, scientists and 2) IT and enabling functions. I think there is A LOT of waste in the IT departments. This is where you have massive contractor budgets, etc. So if you are really looking for budget reductions I would start with:
1) Look at contractor budgets. Those are your CACI, IBM, Accenture, etc.
2) Look at the IT and enabling functions.