My Dream Web Framework, which for a variety of reasons was never and never will be built, has built-in functionality for obscuring IDs in some session-level map, so you can indicate through some sort of type that something is an ID and it automatically allocates some sort of randomized identifier on the way out and converts it back transparently on the way back in.

Thus, not only would DB ids in principle never show in the UI, they wouldn't even be stable between sessions.

This would protect against a number of security attacks. (I don't know what I'd do about bookmarking, though I suspect most apps have a 80/20 solution they could deploy.) DB ids going out to a user really ought to be considered at least a smell, but it's pretty ingrained into our culture.