Comment 2 for bug 811603

There are two uses I can think of for this:

1) To demo different settings. I'm currently writing a WordPress plugin to make it use Libravatar (I know there's one out there already, but I decided to write my own) and Libravatar not supporting the forcedefault option makes it look like my plugin doesn't work right, because the settings page shows all the same avatars.

2) Hypothetically, some site administrators might decide they like the generated avatars, and so don't want to allow non-generated ones. If they switch to Libravatar, any page that displays user avatars would be messed up because Libravatar provides the "wrong" pictures.

So yeah, it's not exactly the most important feature, but it is expected functionality if people are going to replace Gravatar.

On a side note, if forcedefault does get implemented: WordPress currently uses "forcedefault=1" rather than "forcedefault=y". So consider allowing both 1 and y.