The *s mean I've seen them more than once (and the number of stars is the amount of times)
Backstreet Boys**
NSYNC
Sisquo
98 Degrees
Oasis
The Goo Goo Dolls
Jet
Incubus
Angels and Airwaves
Spoon
Jimmy Eat World**
Paramore**
Deftones
Sublime
Hole
Cage the Elephant**
Silversun Pickups
Gorillaz
Linkin Park
The Strokes
Blink 182
Weezer
Taking Back Sunday
System of a Down
Keane
Green Day
Bush
Mumford and Sons
Florence and the Machine**
Eminem
Snoop Dogg**
Dr. Dre
Linkin Park
Radiohead
The Shins
The Black Keys