The main screen have 2 tabs:
Credentials is where all of your online services keeps the information needed to access it (i.e. username, password, tokens, etc.).
You can have as many services as you want attached to the same credential. For example you can have two Facebook services: one for your fanpage and another for your personal page. Both uses the same credential. If you are in a party and want to share to your followers your pictures just enable the service configured to use your fanpage. Otherwise let only the service configured to use your personal page enabled.
Removing a service does not remove a credential. But remove a credential removes all the services bound to it.