Never have done it. Had it done to my squad once at NWAF, that was the last time it has happened. We always have someone( the one without sniper/optics) on ghost duty. Kinda sux he gets to miss on the open field pvp but our sentry always gets one or two ghosters trying.
If your not camping a certain spot/building you really have to shoot to kill, and relocate as soon as you take your kill shot.