You have to be online to choose to go offline first, as it changes some files to work, it wont bother you after that, but every new game requires it.
What are you talking about?
I have just stated that Steam, which has not been able to connect to the internet since April 2nd, has just blocked me from playing all my games, until it can connect to the internet again.
Clearly Steam doesn't offer a true offline mode, but allows the paying customer to be offline for a short period of time, before requiring the PC to 'phone home' and verify itself.
So that is the sort of hassles that punters like me who spend a few hundred quid on games every year have to put up with. Meanwhile, all the pirates get to play for free and don't suffer any such issues.
I would like to continue to pay for games (especially those that I enjoy) but Nazi DRM like Steam and now Rockstar Social Club are really forcing my hand in a certain direction.