Looping the ground is just there for insurance purposes. It just boils down to a matter of preference. I'm not sure which I prefer. Looping adds extra reliability, but I would want to know about any potential problems before they become too serious.
I drew these crappy little diagrams for this
thread.
The green dots and marks represent dead buttons or failed connections.
The green dots represent buttons.
The green square represents a PCB.
This is what you have when you have no ground loop.

This is what happens when the wire or some connection is severed.

This is a break near the PCB.

A looped ground.

A break near the PCB.

A break between two buttons.

Two breaks, one near PCB one between buttons.

A break at the PCB.

As you can see, in a serious failure, it's easier to pinpoint certain problems.