I’ve been throwing myself at Facebook dev for a couple of weeks now and its been… challenging. Not from a “how does this work?” point of view, but from a “why doesn’t this work!” one.
I’m curious as to what “gotchas”, unexpected behavior, or just straight-up bugs people have been seeing doing Facebook work and what they’ve done to compensate.
My current albatross is the (beta) DataStore API; its quite unreliable. Calls to getObject can fail with partial returned values, so that an object with fields {foo, bar, val} created with values {1, 2 3} could conceivably return {1, 0, 3}, {0, 0, 3}, etc. I’ve yet to find an acceptable work around.
Runner up is the inability to use <fb:if-*> on a user’s profile page. I’ve compensated with some truly twisted english and <fb:visible-to-owner>.
I have run into several when creating a Desktop Application, I ended up creating a special Desktop page on the Facebook Wiki to make it easier for others. The two biggest ‘gotchas’ I found were getting the app to show up as a ‘desktop app’ on the users setting page in Facebook and having the desktop app log the user out of the browser session in addition to the desktop app. The answers are on that wiki page.