Since others said it, I will put my two cents in here too ..
When I was still pregnant, DP and I talked about the possibility of something like this happening. We were worried that Child Services might be called on us for various reasons (home birth, no ped, not vaxing, his father hates me and will do anything to make us miserable). We both came to the conclusion that, if need be, we would pack up in the middle of the night and leave. We'd go to Canada first, as that is easier, but we would probably end up moving to Europe. I'd like to live in England or Italy, as would he, but he wants to go to Ireland.
So yes, we would be gone in a flash. We've both moved around the country enough to where we can deal with leaving friends behind and keeping in touch through email and now the lovely invention of facebook. So really, there's not much keeping us here.
I certainly hope this never happens, but it wouldn't surprise me. The Patriot Act already mimics Hitler's Enabling Acts in an all too familiar way. But now that Bush is out of power, we may have some hope in getting that reversed. Our constitution has already been comprised by the Patriot Act so much, that something like this could happen. And it terrifies me. Absolutely terrifies me.