To continue this fight endlessly, I think Ezra Klein is completely misinterpreting the fact that higher-skilled workers get more vacation. There's a tradeoff between leisure and income. The more income you already have, the more interested you become at the margin to have more leisure rather than more income. We can see this from the exciting world of journalism, where the appeal of, say, earning $150 writing a Comment is Free piece instead of watching your The Shield season one DVD is going to have something to do with how much money you're earning from other sources.
This brings us to yet another problem with mandatory vacations -- it's regressive. Leisure is a "superior good" the kind of thing people put more value on the more money they already have. Working class people struggling to earn enough money to pay the bills aren't going to be made happier if they have more time off but earn less money. The sort of pernicious status competition cycles that Ezra postulated as the reason we can't leave this up to the free market are going to be most applicable way up near the top of the income distribution -- it's very plausible that Rich Lawyer A is putting in the hours primarily to show up Rich Lawyer B, but Convenience Store Guy is putting in the hours because he actually wants the money.
This all goes back to the issue of whether or not there's really such a thing as paid vacation. If you believe that additional vacation days procured for people through government mandates won't result in proportionate decreases in their money income, then of course mandating more vacation time is a good idea. Similarly, if I thought that mandating that all employers provide their employees with free cable wouldn't result in a proportionate decrease in their money income, I'd favor that, too. But the world doesn't work like that.