I'd like to see a flexible bollard warning drivers off them, but I think they do the job quite well. Ultimately (of course) it's down to drivers to not hit them, just as they're trying to not hit walls, barriers, sand traps, astro turf etc, much of which can inflict great damage and are positioned just as close to the useable track.
I suppose what I don't like to see is drivers pushing their luck with track limits until an official warns them. I'd much rather they drive to physical limits and see immediate consequences for pushing it too far. It would be rubbish if they penalised cars for crossing the lines at the left hander here where they run out to wall, much better to let them drive to the track limits and hit the wall if they over do it.