[heldtogether]

Having something rammed down your neck like you're a 10 year old never really helps. Being a victim helps people remember the basic things. Have a couple of people walking around placing stickers on laptops that are unattended. When the owner returns they'll see a sticker saying something along the lines of "your laptop has been stolen", and they'll quickly feel foolish for dropping their guard.

[vacri]

That sticker solution is much more '10 year old' than a general warning to watch out for your own stuff. It gamifies the situation, rather than being direct about it.