If you have Steam I'd like you to participate in a short test.
1) Check Steam to make sure you Steam client is up to date.
2) Shut down Steam.
2) Disconnect your router.
3) Start up steam.
4) See if Steam gives you the option to start in Offline mode (this may take a little time initially I've found)
5) reconnect your router and report back your results. (Yes it started/No it didn't)
This is a public poll, so voters names are known. No votes made without further explanation will be discounted.