I never understand the negative reaction when someone suggests basic security measures, there always seems to be someone with a knee-jerk "how dare you blame the victim!!!" response. No one is blaming the victim or excusing whoever the criminal might be, obviously someone that goes into a place and steals is the a-hole in the scenario. But, I fail to see how suggesting measures beyond having a "No Admittance" sign is somehow wrong. If someone burglarizes your house a couple of times, do you stick to your guns and say "no, the thief is the bad guy, I had a sign up so I shouldn't have to put locks on my doors" or do you spend a fairly small amount of money and put a deadbolt in? I, for one, believe that the thief is the bad guy and I should probably take some basic measures and put a lock on my door. Despite our best intentions, signs don't always work to keep people away from "attractive nuisances," that's why, for example, you can't just put a sign by your pool, you are expected to put a fence around it (because children or adult idiots might ignore the signs to get to something they really want to see/do).
Even the most basic lock to get into Cranium Command (or other closed areas) would also deter any future urban explorers, because that ups the risk from "probable trespass notice" to "breaking and entering."