I noticed the first one earlier today, but with two it's worth a post.
UPDATE: Note an adjustment of the title. I think that's more fair to Matt.
First he's criticizing Virginia Governor Bob McDonnell's decision to fund transportation with a sales tax to replace the gas tax. Yglesias calls it the worst idea he's heard in a long time. Yglesias likes things like gas taxes because they promote things like high-density land use and of course they have their environmental benefits. He says the sales tax is more regressive. Regressivity is easy to solve with things like EITCs, but he's wrong to point to the fact that the carless population is largely poorer as a source of regressivity, because McDonnell is also proposing raising vehicle registration fees to make up for the lost gas revenue.
When I first heard it I thought it was a good idea because I assume a sales tax would raise proportionally more revenue from the Northern Virginia and Hampton Roads area where a lot of the transportation budget is going. This is the intuition of Joseph Henchman of the Tax Foundation too. That's a good idea, and it's fair in my book and it's not going to keep getting eroded like the nominal gas tax is. I'm not sure Yglesias take on this is cognizant of the circumstances in the state.
Second, he's an asshole for what he said about James Buchanan. Certainly I've always contended that Buchanan has arguments that are overrated. Even though I like public choice theory, its stronger affiliates overstate the extent to which these insights were new for the rest of the profession. And the value of what he had to say about Keynes was definitely overstated. Being a decent human being does not obligate us to wildly praise everything the man ever did (and to be fair, a lot of the blame for the overselling of public choice doesn't belong with Buchanan anyway). I hope to write more about Buchanan over the next couple days (including more on some of these criticisms) and commenters are welcome to both praise and criticize Buchanan's work as you see fit. But here's a word of advice: if you find yourself second guessing the Nobel committee and the general opinion of the economics profession it's very likely that you have overrated yourself.