A simple security measure
In the light of the Ashley Madison hack, a very simple security measure popped up and it's something that can be easily fixed by any website owner in order to increase the privacy of their users. This measure is the consistency of the message received on the forgot password page.
Most of the websites return an error message if the email entered in the forgot password page form is not found in the database, or a success message if the email is found, which is a very simple way of finding if someone uses a certain website just by knowing their email address. Sure, people might have multiple emails, but this might still be a disaster waiting to happen if somebody's spouse checks their significant other's email address in one of the dating websites.
The simple solution is to return exactly the same message when an email is submitted, and deciding in the backend what action needs to be taken in each case.