gvox
Ghost of Love
U2's openers are usually up and coming bands, not established for more than 15 years (with the exception of special occasions like PJ).
Just off the top of my head Kanye West and Lenny Kravitz were/are certainly not up and coming acts.
Speaking of which is there some sort of source/definitive list online of all the openers throughout U2's history (save going thru each show on u2tours! )