I like much of what Libertarians (and lowercase-l libertarians) stand for: peace; liberty in certain personal choices (the legalization of marijuana wouldn't trouble me); economic "conservatism" of a kind that is often more sincere than that which is proposed by the GOP. But there are a couple of things that keep me from joining their number "officially." The demeanor of many libertarians seems infected with a kind of unattractive ideological absolutism, a sort of "those who are not with us are against us" mentality. Not good. Also, to be frank, the economics concern me a bit. Without a doubt, bureaucracies can be cut, and some even eliminated--but I do believe in a "safety net" for the elderly and the vulnerable among us. On the moral issues, there's a kind of agnosticism I find troubling--but at least a libertarian government wouldn't be funding Planned Parenthood, or coercing Catholic institutions to pay for contraception.
Libertarians are honest, though, and they're thought-provoking. And I gave them a vote 16 years ago. And as for voting Libertarian this November, I wouldn't rule it out. But to become a card-carrying member of the party? For now, dear friends, in the words of Samuel Goldwyn, "Include me out."