I ordered 2 10' cables and coupled them together for a 20' length. It did not work...picture was unacceptable.
Pioneer, as well as the people I ordered the cables from, said that even 10' was pushing it--they were right!
The 3 meter cable that Pioneer supplies is actually 2 cables bonded together, side by side (a control cable and a video cable):

The "control" cable is a DFP (digital flat panel) 20 pin, male to male cable. It is an early type flat panel cable that is being phased out in the PC monitor industry. As far as I can tell, it is used for the control portion of the Pioneer TV/Media Receiver.
The "Video" cable is a "DVI-D Dual Link" digital visual interface cable, male to male. This cable, and the type of signal that it carries, is not designed for lengths over 10', according to everything I've researched. It is my understanding that this cable carries the "Video" portion of the Pioneer Plasma/Media Receiver.
The Pioneer Plasma and the Media Receiver each have female inputs for the two cables.
My final solution:
I got the clients a 50" Panasonic Plasma, with all connections on the TV itself.
Sorry Pioneer...