I'm not sure what your university library is like, but I would be careful in them. At the UWashington, at least once a month you would here announcements over the PA that a few laptops had just gone missing, and to be on the lookout/careful.
Yeah, but that's all contextual as well. If I'm in Odegaard (non-UW people: the 24 hour library) then I will not leave it out. If I am in the CSE department labs, then I probably recognise a few people in the lab at any given time, so I feel a bit safer leaving out the laptop.
What about the kids less affluent than you? Also just because they are in the university library doesn't mean they're students. My university had huge problem a while back where thieves would wander in, hang around in the corridors looking for people to leave stuff unattended in offices or study rooms and then simply grab the stuff and head out the door.
I have, and my worry stems from how many people proudly proclaim how much they relate to the persona[1].
Today, we have remarkably effective medications to treat depressive-spectrum[2] disorders, which are easily enough accessible to the affluent. The hope I espouse is that people do access them.
As much as I admit to being a cynic, I do believe that people are basically socially well-behaved, if not outright honest. Still, truly urban (as opposed to metropolitan suburbia), dense[3] environments appear to me to have a much higher concentration of those who aren't, so I avoid them in general.
[1] No protagonist, in my view
[2] If I may bastardize the Autism- term
[3] e.g. New York, of course, and, here in the Bay Area: San Francisco, Oakland, downtown San Jose