xhonzi said:
1.a. I have to keep reminding myself that Steam is a single user environment. Mrs. xhonzi and I are playing Trine 2 together (ah, yeah... some classic splitscreening ON AN UNSPLIT SCREEN!) and only I get achievements and whatnot. Not that she cares... but, it's the principle of the thing. At any rate, I've only really purchased single player games that will be played (or not, as is so often the case with Steam) by me.
Steam recently announced Family Sharing.