Require a credit card and display said information (anonymized to an extent) on the landing page after they log in. People will be very unlikely to purposefully

Require a credit card and display said information (anonymized to an extent) on the landing page after they log in. People will be very unlikely to purposefully give their credentials to your site to the public. This would work at companies too, because most companies would rather not have all of their employees see this information (it'd be more effective if you didn't anonymize any data... but the security implications could be too great, that's a choice for you too make though). It basically comes down to the fact that most people don't mind taking advantage of a business, until it means that they can be taken advantage too. As harsh as it sounds, the most direct solution is to simply make them put themselves at risk of being taken advantage of if they take advantage of you.