Whats that phrase - Been there done that?

http://www.airliners.net/open.file/1177472/M/

"Federal Express" has operated 747's in the past, although why feed 4 motors when 3 will do? As the Whale gets more efficient, maybe the extra cubes and gross wt. will be more attractive.

This from an outsider looking in (said another way - I don't know why).