Mine was that humans are sensitive to social bounds, even when breaking them, while machines are utterly oblivious to them. Society stays together since most people don't steal and murder, despite theft and murder being rather easy to do for anyone determined to, but if someone could build swarms of self-replicating murder-bots, we might want to rethink the physical security thing a bit.

Computer users who don't care about security using the logic of them being uninteresting targets and there being few crooks often end up having their machines automatically infected to serve a botnet.