Another problem for me with shipping is that the fandoms I might be interested in reading about usually have well visualised relationships that are firmly grounded in the characters. So messing with those relationships tends to trigger a "No, no, no! X would never do that! And Y would run away!" reaction. This tends to kill my interest in that story stone cold dead.
I did run across a fabulous, if regrettably unfinished, BtVS/Firefly crossover that made better use of Xander than much of the original material did. It didn't seem to be shipping Xander with anyone though.