You pose a GREAT question that I've thought about a lot. The conclusion I've come to is that most backpackers are cool and you don't have to worry too much about it. I feel safer leaving my campsite "unlocked" in the woods than my car in the Target parking lot. But, on the off chance, what I do is to make sure that when I do a dayhike from base camp, I always bring the essentials: wallet, car key, etc. I can buy another tent or sleeping bag but I would be SOL if someone took my wallet and keys. Those are my main concerns. I'm curious to hear other people's concerns/strategies.