You have to hand it to him for being so honorable. I think he knew there wasn't a good chance he'd make that money back, but he didn't want to screw his investors. Evan Williams is a model entrepreneur.
From what I gather it seems like he wanted out of the project. At some point it seems he decided "I'm not really a podcast guy, I'm a Twitter guy" [not a quote]. He did what I think was a pretty honorable thing and took the hit himself. He could have easily shared the loss with his investors. I would of course agree it was risk they signed up for, but he chose differently.
There's nothing honorable about buying high and selling low. It's bad business and if this were the creed of our "model entrepreneurs" the world would be a worse place indeed.
Until today it's funded by Evan Williams who bought Twitter and Odeo from it's previous investor last year.