How can I turn off Facebook IM permanently?
The newest version of the Facebook app does not include chat.  You can uninstall or disable the Facebook Messenger application to keep IM from running.



In the older official Facebook for Android app, you can shut off chat via the following:


Start up Facebook
Make sure you're in the main menu (press Back if it shows the news feed)
Click "Chat"
Press the Menu button and hit "Go Offline"