I'm researching implementing UUIDs in an app for the first time, and the very first thing I want to know is 'what is the probability of collisions'.
I think it's an incredibly important software engineering question, yet it seems to be closed as 'off topic'.
Counter argument: "is't it obvious that if the whole software world is willing to use the standard, then you can assume you're going to be safe too? Not necessarily, some methods for migrating existing (incremental) identifiers to UUID's merge existing incremental IDs with the UUID, so understanding how probable collisions are in the UUID helps one to understand how probable they are in an identifier that is part UUID and part incremental ID.
That's one example, but there are obvious reasons to do with wanting to understand the software you're building in the general sense too.