So yes - a great point. I just wanted to push the discussion a little farther than laughing at people promoting this pipe dream to thinking about what an appropriate reaction would be. My reaction is decidedly utilitarian because I've never really been put through this. If this were to actually happen, I might say "F*$& it - let them go". I don't know.
What I do find entertaining is a lot of libertarians and anarcho-capitalists who always talk a big Lysander Spooner game when it comes to the state in the union suddenly don't have a problem with states declaring secession and imposing that on all their citizens.
Finally, I agree with P.S. Huff that discussions like this are healthy. It's also nice to discuss seriously to get peoples' minds past just thinking about the Southern Confederacy. I've said before that I think the trend is going to be towards federalized, global government. But on the way to that end state it's entirely plausible that we'll see realignments and such. So it's important to think through this.
UPDATE: More from P.S. Huff!! I apparently committ "old fallacies"! He's a little vague, but I think my "old fallacy" is that I don't repeat grade school (and I mean the low grades - I'm sure by high school we were talking about it differently) gauzy feel-good history. Somehow that doesn't feel like a "fallacy" to me. George Washington and Thomas Jefferson were traitors to the British crown. Thank God they were. If it weren't 8 in the morning I'd propose a toast to treason right now.
Jonathan also has thoughts. He writes: "Treason can exist in many forms, and secession ought not be one of them. At least, if we define secession as an act of treason, therefore implying that seceding American colonists committed treason against Great Britain, we should admit that defining secession as treason is not a good argument against it." Right. The revolutionaries were most definitely committing treason. I don't think there's any question about that. And I can't really blame Britain for responding how they did. Granted, there are differences in circumstance (some of which I highlighted a couple days ago):
1. We could plausibly pull it off
2. Unlike the Southern Confederacy, it wasn't a dumb idea, and also
3. It was a justifiable response to British abuses in a way that I'm hesitant to say for the Southern Confederacy or secessionists today. Secessionists today are treated as full citizens. This wasn't true of the colonists.
Granted, it was still treason. I don't think treason has any necessary moral content to it, but it does structure how political institutions respond. Britain could have quite reasonably said "yes they're committing treason but it is expensive to maintain this colony and we've been leeching off them anyway so in the interests of justice we should let them go - we have never accepted them as part of our political community despite their desire to be a part of our political community, so we have no business demanding they stay". You can't have that response to modern secessionists because they have been full participants in our political community.