I believe the reason ports on laptops are on the side rather than the back is that Apple prefer its users not have to reach to the back or turn the laptop around to plug a cable in.
Apple may prefer that...for now. I've owned Apple laptops that had ports on the back before. A 520c. It's much nicer for keeping the desktop clutter free, but not as good if you are using it on your lap.
Reaching around the back of a machine that is about the size of an a4 piece of paper is not much of an effort to make
But like I said. The thing HP has done is worked out a way to have just a small amount of the computer thick enough to house ports and a cooling system, allowing the rest to be really thin.
I've been looking to get a MacBook so I don't have to carry my MacBook Pro 15" to work every day, but that means a massive drop in CPU performance.
This HP design gets an i5 or i7 in there while being 3mm thinner than a 1.2gHz MacBook. That's an impressive design.
Apple needs to lift their game. The MacBook Pro design is starting to look and feel it's age.