This is why I'm a big Steam guy. I love being able to log in and just DL everything. Of course, I do keep an image of ALL my games installed/backed up in case the apocalypse comes and the Steam servers go offline.
Hehe, if the apocalypse comes I'm pretty sure that you wouldn't worry much about your games anymore when the buildings next to yours are reduced to cinders and your own legs are stuck under a ton of destroyed concrete while the remnants of your computer's smoke intoxicate your lungs.
But seriously however if Valve ever have a major problem with their servers I really do think that they would release some sort of a patch that would allow the last version of Steam to operate off-line and without any additional updates ever again, they can't just turn the switch off and leave everyone in the dust, or else I'm just being extremely naive and seeing things with pink glasses, if that's the case and if we could really "lose" access to our Steam games if Valve ever explode tomorrow then I would certainly become the saddest panda on this planet.
And, OP, digital purchases of games is your own solution, but in the end your logic isn't necessarily restrained to disc drives, what I mean is that digital gaming distribution or not all the software needs to be stored somewhere, either on HDD's, or on USB Flash Drives for instance... and that hardware also fills up land fills eventually, remember what science tells us all the time; nothing is created, nothing is lost, everything is transformed. You'll also throw your HDD or your USB Flash Drive away one day or another... you know... because we humans have that tendency to not being able to create things that last forever, it's been the case for a couple of hundreds of thousands of years now.