What about conspiracy charges and bank information reporting requirements? It seems to me that if we take a pure "harm" approach to the law we will find ourselves unable to successfully police serious problems like organized crime. We often complain as citizens that the police are unable to protect us until after something terrible has already occurred. Laws aimed at deterrence and prevention by criminalizing conduct that precedes the actual harm causing activity are one way to meet that problem. We have to be very careful, but I think the balance is worth striking. We didn't start out criminalizing actions that don't cause immediate harm, but our experience has led us to do so in response to live threats.
Yes, I'm a very poor libertarian. More of a law and order type with small government leanings.