The biggest barrier for me is that I am fearful of the executive branch of the government having my directly-given opinions about subjects which may be controversial. How long before some analyst starts saying, "I bet people that care deeply about closing Gitmo, legalizing X, and dismantling Y are more likely to be domestic terrorists!" -- and then I end up on a no-fly list or something.

If it comes to that (and granted, it may), not being able to fly easily would be pretty low on my list of worries.