Since Fareed Zakaria's The Future of Freedom came out, there's been renewed talk about the pitfalls of democracy. Specifically, the problem of concern is that democracy and liberalism (in the broad sense) don't always go together. The obvious cases are the election of Hitler and the feared Islamist victory in a democratizing Middle Eastern nation.

I haven't read Zakaria's book (though I'd like to, as I enjoy his columns), but the general idea seems rather obvious, and applicable in some degree to any political system. The issue at hand is that liberalism is an end, whereas democracy is a means. Liberalism is a way of organizing society, whereas democracy is a way of making decisions about how to organize society (the distinction is a bit fuzzy because democratic institutions like voter registration and electoral districts are ends required to be able to exercise democratic means). No means guarantees a certain end, though it can make some more or less likely.

Thus, if you focus on the means, you may find them producing ends you don't like (as I mentioned before). And conversely, if you focus strictly on the ends (narrowly defined, as participation in a certain type of decisionmaking process can be as important an outcome as the decision reached), you could wind up using some pretty unsavory means if others fail to produce the right ends. Which is why liberal democracy is such a balancing act (as is, say, a dictatorial theocracy -- you have to make sure the despot makes doctrinally correct decisions while retaining power).