Facebook is possibly the most complex social app we've ever used in the history of apps development. 200MB is nothing when you put it in perspective.
Give me a break. It posts pictures, has few buttons, chat etc. and to the extent these take up memory, it is because Facebook is in a rut of adding features most people don't use. I want a place to post updates on my wall and exchange thoughts with my friends and family, not an alternative operating system, which is what Facebook is trying to evolve into. Moreover, I'm pretty such much of that memory is dedicated to marketing of one form or another. It takes nearly 20 seconds for FB to load on my phone, even from a fast internet connection.