Comment 10 for bug 881219

Some plausible use cases for being genuinely offline as far as IM is concerned:

* I really, really don't want to be disturbed (but still need a web browser)

* I'm on a sufficiently flaky network connection that if you send me a message
  there's a good chance it'll just get lost (most IM protocols don't have
  application-level acks, so there's a ~30 second window of message loss
  every time you drop off the overloaded conference wifi)

* Using a particular network connection for some/all IM protocols is expensive
  (either in terms of money or battery capacity - 3G can be both!)