I kinda think that there isn't really an "official" sources.list for Debian. It depends on how the user wants to set things up, I think. For example, I don't use the "deb-src" lines; my sources.list looks like this right now (I don't even have "non-free" and "contrib"):
The last line is for the SpaceFM file manager. This is on a Wheezy installation that I've been running since September.
But I'm not sure about the importance of including the "wheezy-updates" (the former "volatile") line. I did find this announcement, from when they went from "volatile" to "squeeze-updates": http://lists.debian.org/debian-volat.../msg00000.html
Reading that, I'm thinking that including "wheezy-updates" wouldn't hurt, but it probably isn't necessary. I'd be interested to read any opinions on that.
By the way, as of this writing, the Debian Sources List Generator hasn't been updated for Wheezy being the current "Stable." But it's still useful to take a look at that site.