It's always a pleasure when a company offers a public bug tracker for users and third party developers. So it's great to see that Facebook has a public bugzilla.
The problem with having a public bug tracker is that you're supposed to be responsive and fix bugs; nothing worse that real bugs rotting in the tracker because the group behind the product doesn't really care about that specific bugs.
So far I've filled a few bugs for the Facebook API:
A security bug, letting anyone deactivate feed templates for any app (fixed)
5159: Incorrect error code returned for Stream.get - I can't believe they won't acknowledge it's a real bug!
5624: Stream.get is not really using the updated time. In short, we miss data because the query doesn't do what the doc says it does. They do recognize that should be fixed, but didn't put a very high priority.
I have also filled a few feature requests, but it doesn't really matters: they have obviously no obligation to implement them. On the other hand, it would be nice if they fixed the bugs even when they're not security issues.
One interesting thing I've noticed is that not only they have a public bugzilla, but the code source for their API is Open Source. Let's see: "Facebook Open Platform is a snapshot of the infrastructure that runs Facebook Platform. It includes the API infrastructure, the FBML parser, the FQL parser, and FBJS, as well as implementations of many common methods and tags."
Cool. That means that if I'm motivated enough, I could fix the bugs and submit a patch! Let's look at the buggy Stream.get method... Wait a minute - that source code is just a tiny subset of the Facebook API! Oh crap. Looks like I can't fix it.