I was sitting back thinking of all the large corporations that bolted from Michigan over the years:

Pulte
Comerica Bank
Spirit Airlines
Electronic Data Systems [[?)
Volkswagen of America
Bluware
The Ford Foundation [[not a corp per se, but a major philanthropy institute)
Discount Tire Company
Kmart

That's about all I can think of at the moment. Please feel free to add anymore you can think of. Which loss hurt you the most?