The USB ports are close together because there's very little space in the MBP case design to fit all the ports into. If you look at what's inside the case, you'll see at a glance that the right edge of the case is fully occupied by the optical drive and hard drive; the front edge by the hard drive and the battery, the back edge by the display hinge, cooling vents and airport card (inside the hinge cover), and only the portion of the left edge that isn't occupied by the battery is left over for ports.
There are many USB devices and plugs that are narrow enough to use side by side in the MBP's USB ports. You need to be careful to buy those from now on, not just any USB cable, flash drive, etc.