Trevor has a post about avoiding classifying yourself. I basically agree with what I take to be point of the post. I don't want to feel compelled to agree with Ayn Rand lest my libertarian decoder ring be confiscated, but I think there's a confusion here.
I feel that I don't really classify myself as a libertarian, that's just what I am. A libertarian is someone who has certain beliefs, values etc and I share enough of them to be a libertarian. Someone who doesn't eat meat simply can't help being a vegetarian.
Trevor worries about feeling the need to defend the principles of your box, but I personally hope that people like Trevor can be counted on to defend the principles of democracy, freedom of expression and many other things.
Admitting, or even hoping, that your beliefs will mature and improve isn't the same as denying you have them.