Your right the camper vans do give it a tacky feel and probably should be avoided, plenty of spectators should without doubt be given serious thought by PD, now some people say they wouldn't even notice because they are to busy focusing on the track, well i am not so sure that works for everyone, spectators will give atmosphere to a track, and while i don't spend all my time looking at them, I do seem to pay much attention to it in the subconsciously, I find myself getting bored of certain tracks occasionally because my opponents slightly too easy, so there is nothing exciting about the race. I run faster in sports competitions mostly because, of adrenaline, but encouragement from spectators always makes me push harder. Now I am not saying spectators will encourage everyone to work harder, nor am I saying you will be able to get the 'atmosphere' over on your TV, however this doesn't take away that spectators play an important role in racing.
I wouldn't like to turn up to the Sunday cup and find spectators occupying every possible spot however for the Major races, in the extreme hall and endurance events, I would like to see places cram packed with active spectators, this surely isn't an impossible ask for the PS3 and if it is to taxing perhaps inactive spectators, I would rather see static spectators on major events who are just about everywhere rather than a few moving spectators on a major event.