Legitimate uses of browsers' "porn mode"

Often labelled as "porn mode", the incognito/privacy/anonymous mode on browsers can be very useful for web developers.

First, it's very helpful when testing an app with various user roles. You can log in simultaneously as different user roles in as many incognito windows as you need. No need to sign out and sign back in as different users to see what the effect of a change by an admin had on a regular user for example.

Second, similar to the first case, it can be used to quickly see what an anonymous user sees without having to sign out. It's useful to see what others will see on your various public profiles around the web too (facebook, github, etc.).