alt Hacker NewsI think more important than worrying about people treating an opaque value as structured data, is wondering _why_ they're doing so. In the case of this blog post, all they wanted to do was construct a URL, which required the integer database ID. Just make sure you expose what people need, so they don't need to go digging.
Other than that, I agree with what others are saying. If people rely on some undocumented aspect of your IDs, it's on them if that breaks.
Exposing what people need doesn’t guarantee that they won’t go digging. It is surprisingly common to discover that someone has come up with a hack that depends on implementation details to do something which you exposed directly and they just didn’t know about it.