There have been a number of posts at LGM recently about the third-party option for disaffected liberals. Loomis, djw and Lemieux have all posted about it.
And you know, I think Loomis (who's the leftest writer on the site) has a point. Most of the progressives who plan on not voting for Obama* are privileged white dudes, and that has a lot to do with the way they frame the issue of voting. They're secure enough from the worst effects of a Republican government that they can afford to vote symbolically.
I think the same effect was pretty prevalent during a lot of the administration's legislative sausage-making. People with white collar jobs and good healthcare plans saying they should have gone for single-payer come hell or high water, people with job security saying unemployment insurance wasn't worth a temporary extension of the Bush cuts, etc. Liberals on the Stoller/Taibbi/Greenwald axis, for the most part, are not organizing because they feel directly threatened, but because they are committed to a certain political philosophy, and are generally leading secure enough lives that they can afford politics as a passtime.
That's not to dis middle-class political amateurs; that's basically my tribe. But I think it really behooves liberals such as myself to remember that the fights are really not about us, they are about the actual effects government can have on people's lives. If you're gonna vote to make yourself feel better by associating yourself with a person or group you admire, that's your call. But you don't get to lecture other people about their vote, and you don't get to claim to be some sort of pure True Liberal while turning your back on those less fortunate than yourself.
*Exceptions for people who are in safe states and trying to get the third party of their choice to the 5% threshold or whatever. We're talking about people like Matt Stoller who argue that the two parties are indistinguishable and that costing Obama the election wouldn't be a bad thing.