That FB app(http://apps.facebook.com/funnyqa/) is totally out of curiosity about how FB developer platform is working. Roughly it is like this:

• Get started cost  -- ~10$/year for a website space; need a PC of course
• Technology platform -- LAMP. Website host provides it as a bundle for free. I choose this platform instead of .NET because of (1) PHP hosting fee is much cheaper(less than ½ of ASP.net), (2) PHP lib is official supported  by FB while .NET lib is maintained by community only, (3) Sample is for PHP by default, (4) In FB app developer forum, most people talk in PHP
• Ramp up time -- ~ 1 week for basic fundamentals such as lib, FB API, FBML, how to publish, set up ads, etc. Of course I am familiar with LAMP which saves me much time.
•  Development time for my app -- ~ 3 days. It is quite simple app. actually most popular apps in FB is very very simple. If an app takes users more than 15 sec to figure out how to play with it, it would not be popular definitely.
• Promotion -- I didn’t do special promotion, just list in FB app store and set several key words. Dozens of my friends installed that app.
• Monetizing -- take less than 1 hour to get AD code from Cubics, an advertizing delivery  closely bundled with FB.

I would say the whole experience is pretty enjoyable. My score card to evaluate a developer platform is (a) First run experience - how long it takes to get “hello world” sample working and do most simple customization. (b) How long to get answers for my questions, (c) how easy for my app to reach potential users, (d) how easy to monetize my app if $$$ is my goal. Obviously FB is doing great job in all of above aspects.