Twitter, the twee San Francisco messing startup, is all hope, no revenues. That makes it irresistable to Silicon Valley's best and brightest — like Google's top designer, Doug Bowman, whom we hear Twitter just hired.

Why is a designer switching teams such big news? Jason Fried, the influential founder of Web-software company 37signals, hailed Bowman's 2006 hire as Google's "best acquisition to date." Google even created a grand new title for him: "visual design lead." But now Bowman's leaving after less than three years.

People switch jobs for all kinds of reasons. And Bowman had to work for every designer's nightmare client, Google executive Marissa Mayer. But Bowman, a veteran of the industry who pioneered Web design at Wired (where we were briefly coworkers), is a telling barometer.

Earlier in this decade, in the midst of another downturn, Google was the black hole for Silicon Valley's most talented people. Two years ago, it was Facebook. Now Twitter — a revenueless startup with just 30 employees — is the startup with the pick of the litter.

Talent has always flowed this way in the Valley, drawn by money and hype and the shared belief that a small group of people can, through sheer force of all-night coding sessions, change the world. (Change the world, that is, from one in which they are poor to one in which they are rich.) Here's to Bowman keeping the dream — or delusion — alive.

(Photo via Fawny)