eisberg77: No, this is more about the truth. And Installation method is not in any way shape or form a DRM. You download your game, you can play it without a client running, without the internet, therefore it is DRM free. Half-LIfe 2 is DRM free. All single player games on Steam can be played in Offline mode if they do have DRM, but you will never be asked to go online once you run it the first time.
You must be joking or just managed to avoid all the forum wars about DRM where the offline mode's bad habit of only working when you don't need it has been confirmed again and again, year after year.
Half-Life 2 may no longer require the Steam client to work, but the days when that would have been enough for me to buy it are long gone. Nowadays for a publisher to even hope to sell me a game they need to offer an official DRM-free version of it.
mechmouse: Someone once told me you can copy the entire Steam folder from one machine to another and it will just work. Personally I didn't believe them, but I did test it. And to my surprise it worked. Also dependency installers are included in a subfolder.
So I have a back up of the few Steam games, which theoretically should survive post internet.
That said. I don't trust it to not to have issues, and I most certainly don't trust VALVe not restrict offline mode at some point in the future.
I don't know about Steam, but at least Uplay would not let you past the login prompt before being able to access the servers and verify your account. If Steam is the same, then at best your DRM'ed Steam games could survive until you run out of computers where the Steam client has been installed and logged in to the service before the fall.
And this is me assuming that the Steam client stores locally a list of games you have purchased and use that to allow you launch any one of them in offline mode without any online verification even if you copied them from another PC instead of the client being connected to Steam during the test and doing the check on the background.