I've never bought the argument about kidnappings etc, with billions of dollars you can hire people with lots of guns
But when you suddenly become a billionaire, what do you do? Ring up some private security company? You would need to trust them not to screw you over. It's kinda boils down to you not being able to trust anyone, not even governments that might consider you a criminal.
I would feel pretty comfortable calling G4S, Securitas, GardaWorld, DynCorp, Brinks, Control Risks, etc.
Alternative, you call the whitest of white shoe law firms and retain them to find a good security firm for you.