“He Sold His Soul to Wal-Mart,” the cover of September’s Fast Company magazine shouts.

The story inside doesn’t quite pay off the cover tease, but it offers a fascinating look at the life of Adam Werbach. Or at least what it’s been like since he decided to take on Wal-Mart as a client. That alone isn’t newsworthy. But the plot thickens when you recall or learn that Werbach is the former wunderkind president of Sierra Club and once called Wal-Mart “a new breed of toxin.” After a very public falling out with the environmental movement, Werbach was approached by Wal-Mart to help them with their now much-publicized sustainability initiatives. He eventually agreed. And in the past year his consulting firm has grown from eight to 45 employees, mainly to handle the Wal-Mart work.

The article gets to the heart — and soul — of one of the many contentious debates within the environmental movement. Are environmentalists better advised to become corporate insiders to move business toward greater sustainability? Or do they need to remain outsiders to a consumption-based economy that by definition is unsustainable and needs radical overhauling? Perhaps that choice isn’t as stark for the environmentalist who weighs whether to go to work for a progressive company such as Clif Bar. But when it’s the hated Wal-Mart, well, that’s a line most won’t cross. Had Werbach taken on just about any other corporation in America as a client, he wouldn’t be nearly as reviled by his former environmentalist kin.

While I haven’t walked in Werbach’s shoes, I can tell you this: If I had been approached with the same offer from Wal-Mart, I sure as hell hope I would have run away faster than it takes Wal-Mart to earn its first million dollars each morning.

How about you? Is Wal-Mart “beyond redemption”? Would you have stayed in the environmental movement and tried to make it more effective, rather than walk away like Werbach? Or would you have taken the Wal-Mart gig and figure on making a bigger difference there?

These are my questions.

P.S. Thanks to The Triple Bottom Line Blog for the tip-off on this article.