Instapundit linked up this interesting point, which is short enough to be excerpted in its entirety:

What I don't get is this: why was it wrong for Judge Roy Moore of Alabama to unilaterally declare federal law wrong, and defy it by installing a Ten Commandments monument in a courthouse rotunda ... but it's okay for San Francisco Mayor Gavin Newsom to unilaterally declare state law wrong in prohibiting same-sex marriage, and defy it by issuing marriage licenses to gay couples? I mean, I know why the media was outraged by the former episode of grandstanding and not the latter, but as a legal matter, what's the difference?

As a radical Jeffersonian Republican-Libertarian (why yes, I'm reading Founding Brothers, why do you ask?), I have to say I agree with the basic point of an official overreaching his authority, but there is in fact a difference. Moore was an appointed state supreme court judge with (I can only presume) a lifetime term. The Honorable Mr. Newsom is an elected official with a proscribed term.

Mayors have to please people to keep their job, and it's quite easy to remove them when they don't. While the media circus surrounding Moore was mostly about the secular media punching a religious nut in the, well, nuts, it was also the only effective way to call attention to a judge abusing his powers.