Hmm... Josh writes that "coal is an undesirable energy source mostly because... it emits a ton of greenhouse gas." Well, sort of. There are also the mercury and sulfur-dioxide emissions to consider. Plus mountaintop-removal mining, which is destroying broad swaths of Appalachia. Then there are all the miners who die or get injured each year. Not to mention the industry's penchant for undermining safety regulations and busting unions at every turn. Jeff Goodell has covered this at length, but it's no mystery why people dislike coal.
Now, global warming is the elephant in the room, but given finite resources to tackle the problem, it's not obvious that carbon sequestration is the horse to bet on. As Markey noted today, the DOE doesn't expect sequestration to be viable until 2020--if that. Utilities would also have to re-jigger their existing plants or build new ones, while putting in place a vast array of pipelines and monitors. That's no "stopgap solution." (A real stopgap, by contrast, would be to make improvements on the efficiency front--there are a ton of very simple things the United States could do right now to drastically reduce its energy usage at little cost.)
And clean coal is hardly the clear-cut energy of the future. As Joseph Romm points out (channeling the GAO), even if it is ready a decade from now, it's going to be pricey--up to 78 percent more expensive than electricity from dirty coal plants--and at that point may not be cost- competitive with solar or wind, if current trends hold. It's definitely an idea worth researching, but that doesn't mean Congress ought to lavish the lion's share of subsidies on coal while skimping on, say, solar or energy efficiency. Then again, there's no Big Efficiency lobby out there...