This would be bad; we've already had a few cases on HN where someone noticed that they could increment the customer number in a URL or similar, resulting in police action.
IDOR is a well known security issue that can result in exactly the scenario described (someone incrementing a counter in a url) and has on many occasions in different jurisdictions caused legal issues for the person doing it. Unless you are specifically asking for a hn reference, which I don't understand the relevance but I'm sure they exist.