The TIME 100

John Mayer doesn't radiate courage. With his sunken eyes and a wardrobe you might generously call agoraphobic chic, his aura of passivity is an artistic achievement. Factor in Mayer's Grammy-winning ode to helplessness, Waiting on the World to Change, and it's tempting to dismiss the 29-year-old as the latest figure in a disturbing cultural phenomenon: the rock star as wuss.

Listen to his music, though, and you'll discover that Mayer wields sincerity like a pitchfork. His empathetic voice and emotional fearlessness elevate songs like Your Body Is a Wonderland and Daughters from pop ballads into more meaningful territory; give them half a chance, and during vulnerable moments, they'll be your friends for life. Sincerity has also led him ably down the mine-strewn path (for a white boy from Connecticut) from pop to the blues. Mayer may never have seen the inside of a juke joint, but he knows that the blues are less about melanin than about truth and technique, which explains why Eric Clapton, Buddy Guy and B.B. King have called on him for guitar playing that matters.

Mayer has friends in some very odd places—go on, name another person with Steve Jobs, Kanye West and Jessica Simpson on speed dial—and where his burgeoning celebrity may take him is a subject he ponders in a good regular column for Esquire ("Music Lessons with John Mayer") and on the only musician's blog not written by a publicist. If reading's not your thing, check out his response on YouTube to Ryan Seacrest's questions about Simpson; dude's pretty funny too. Whatever waits in his future, you can bet Mayer will find a way to sing about it truthfully.