well, ya can use it if, say you have this empty tank but dunno (yet) whom is going to getin as... say, gunner or alike. Then (if we wanted a *HINT*when gunner is inside) ya use the format phrase which basically tell the game engine to investigate and use the NAME (identity) of whomever gets in as gunner.
script example:
(script is executed in tanks INIT field) : [this] exec "TankScroll.sqs"
=============================================
_tank = _this select 0
_g = (gunner _tank)
@ _g in _tank
Hint format ["%1, Get out\nthe tank is burning!!",name _g]
=============================================
som'n like that anyho'
(VERY close to what planck said) *cough*
allthough 'twas the "name _g" part that tells
the engine to go looking for the gunner's name
;D