The number two issue is they change the API and don't announce the changes until people start posting questions asking why something is failing.
Number three is random failures with no error. (Did they change the API again or is it just a random recurring event?)
Let me publicly say something I've said privately: I will pay up to $1000/year for a subscription to a service that 1) documents the facebook APIs, 2) monitors examples and common usages and lets me know when they stop working, and 3) provides a weather report for the Facebook API servers letting me know when they're slow or sick.
Heck, I might pay more. We waste far too much developer time dealing with the problems Jobu so rightly points out.