Once upon a time my perfume was stolen from my bathroom cabinet during a party. Upon talking to folks about this, I learned that many people look inside bathroom cabinets when at someone's house. This horrifies me. I have never done this at anyone's house. I haven't rigged ours to drop marbles if you open it, but I might, so open at your own risk. Also, If we have good drugs we're not going to keep them there.
PS: Our bathroom has a graffiti wall. Spend your time putting something memorable there rather than looking through our cabinet.