Justin Timberlake, here with gf Jessica Biel at Hollywood Bowl, continues to wear his own label and the personal endorsement seems to be working. As sales continue to decline for celeb labels from Jennifer Lopez and Victoria Beckham, William Rast is among the few that thrives. Gwen Stefani’s L.A.M.B., Nelly’s Apple Bottoms, and Beyonce’s Dereon also continue to be successful, while Paris Hilton and Heidi Montag have been forced to close shop on their short-lived lines. So what decides it, star power or quality of merchandise?