Should I have multiple cable runs for a room, or just one?
I doubt most buyers will even notice or care if it was pointed out to them.  Today, everyone uses a cordless telephone, wifi for networking, and any cables are just run around the baseboard.  And I say this as a geek that ran conduit through the walls when I redid my basement.  Speaking of which, if you ever remodel (or build) something you plan to stay in, run conduit through the walls.

The key point you need to keep in mind is that it should be possible to get to a majority of the walls along the baseboard from your wall jacks without passing a door or closet.  If a large wall could be used for a TV but requires running the wire over the door, then I'd put a second jack on that side.

My guess for apartment owners is that two jacks results in less wires over carpets or nails holding wires everywhere, so they do this more to reduce damage than to make your life easier.