> But how many people will check in detail what‘s submitted? That's a valid criticism. It only takes one person finding clear evidence of problematic behavior

> But how many people will check in detail what‘s submitted? That's a valid criticism. It only takes one person finding clear evidence of problematic behavior to advertise that fact to the entire community. So long as a small fraction of people do actually check, the whole community will be fine. But if only a negligible number of people check it, then perhaps no one will be checking when it is abused. > And again, how do you prevent that different users get different functionality? Well, it depends on how the system is discriminating among users. To a great extent, that kind of abuse is prevented by anonymous users. You don't have to log into HIBP in order to use it. The system could still be discriminating by IP address, or even by various kinds of browser fingerprinting (including just collecting the advertising company cookies that so effectively eliminate anonymity for much of the web). Occasionally using TOR won't help against this -- a malicious operator could simply provide "clean" functionality to all TOR users. - - - - On the whole, things like, k-anonymous API design, making source code open, or having a small fraction of users checking for security issues all help a great deal and make it difficult for a malicious operator to abuse the system. But none of them are perfect. In the end it comes down to trust. Troy Hunt has EARNED that trust due to his openness, and in no small part by choosing to implement protections like these that he didn't need to implement, and I find that extremely persuasive. If you take steps to ensure that your CANNOT cheat your "customers", then that's pretty good evidence you aren't likely to be trying to cheat them.