I mean, maybe, although usually they aren't a perfect sequence. I just have a hard time imaging a scenario where that information is so private you're worried about leaking it.

>Also, sequential ID may reveal some information you may not wan to share. If someone's user ID is 1234, that may be an indication the service has at least 1234 users.

You'd just start at a million or so, +/- some random amount. That's not a new thing. You should be able to spin all of the auto-number types in all the databases to whatever you want it to start at.

Timing based UUIDs (type 1) or ULIDs can leak (surprise!) timing information. If you can see them then you can infer the rate at which some resource is being created. For example the rate at which a service is creating users or business transactions. This can be valuable competitive information you don't want to share with the world.