[pestatije]

It forces the use of a new password specific to that site. Reusing passwords is considered bad for security.

[joshenders]

Can you elaborate? It seems like it just enforces a specific type of password which is entirely reusable.

[wizofaus]

Yes but that's a terrible way to enforce it. I've said here before I'd actually like the browser to forbid users from reusing passwords when signing up to new sites. I'm guessing there is actually a plugin that does it.