[stipes]

Thus the reason the AGPL was created, although hardly anyone uses it (to my knowledge).

[ramanujan]

Diaspora is on the AGPL, so that Facebook won't be able to use their code.

[_delirium]

There's a reasonable number of projects using it, though not nearly as many as other licenses. Some that come to mind: Gitorious, Launchpad, OTRS, MongoDB, StatusNet.