I'm a fellow car nut too. I use to enter in the NSW hillclimb comps, drag racing and the occasional track day at wakefield and oran parks. After an accident, I woke up to myself and swapped hobbies to the slower pace of 4WD'ing and I'm loving it. I miss going fast but at least it won't kill me.
Generally the people out there
are respectful of your property and are there with the same intentions as you, To have fun. The only theft you really need to worry about is from the local wildlife. I've had possums scratching at my tent to get to a loaf of bread and a Kangaroo eating some uncooked pasta off my table while I was having dinner. So LOCK UP YOUR FOOD, you have been warned!!!
Returning to a campsite after a walk, I noticed someone had moved my table. It turned out to be my 'neighbour' because he saw that it had blown over. At Stockton beach I burried my 20L drum full of fuel in the sand in case passerby's saw it, but left everything else out. The only place I had my wallet stolen was at a van park in Rockhampton QLD. I saw a couple of young aboriginal kids playing on the swings and I didn't think to lock up the cabin. There was only $20 in it, but the inconvenience of losing my cards and license ticked me off.
In general, a bit of common sense prevails. I keep my pantry/food, wallet, phone, GPS and anything else valueble hidden and locked in the car. It also depends where you stay, If there are a few yahoo's like me about, you might want to lock up your beer.