How quickly we forget the most controversial move in all of pro sports, when the Browns left Cleveland and became the Ravens, playing in the Colts' old city!
Arguably, that lands in #3, after the NY Giants' move to San Francisco (because of West Coast expansion) and Irsay using moving vans to move the Colts (because...moving vans). But I feel the Cleveland-Baltimore move of 1995 was one of the saddest ones; due to the immediate mid-season announcement, followed by the decay of player (not personal) morale, sponsors pulling out, and once-rabid fans not willing to show up.
I wonder if something crazier or stranger to a moving sports team has happened outside America. One or two racing teams have done some bizarre things, but that's for another forum*...besides, moving around is naturally part of the sport.
* In the spirit of this very non-thread thread...
Andrea Moda Formula Fans.