My app will be in flash but I'm not sure where to start. Do I just build the app in FLASH with server backend and stuff and than build it into the MDP or is it something else? This is my first time building an app for any social networking site so I'm a little new to it.

I don't work with Flex and don't have any plans to start. I've heard of solutions using a Socket connection in a "brew your own HTTP" fashion, but I haven't looked into it yet. There are changes coming down the pipe for the Flash player that are going to make setting up security...