I would love to have a physical storage of the game, but I hate discs. Discs are slow, fragile. I think the future lies in non-volatile memory like NAND Flash memory, used in SSD and memory sticks.
And this is a strong possibility if and when USB 3.0 is accepted standard by the industry. Faster than discs, can be driven over many times by a car, trampled on, and still provide the same data undamaged.
I store my old gaming boxes from 1994 (Tie Fighter, Normality etc) in my parents' garage attic. I don't keep any game boxes in my apartment. Of course, I have fond memories of them, but having the boxes around isn't doing me any good.
Until a USB 3.0 flash unit is used in the games industry, online storage like Steam is much more convenient for me. I prefer to have books in my shelves rather than game boxes with manuals.
Problem with online storage is that not everybody has a good broadband connection.