No. Needle exchanges do not curb drug addiction. Needle exchanges simply make the drug addiction a little bit safer. The question should be about how much safer, and at what cost. The costs of up-keeping needle exchanges could be better implemented by paying for rehabilitation in an approved institution for those who truly want to get clean.
Needle exchanges do nothing to help drug addicts with their drug treatment. The only positive to needle exchanges is that it will help prevent users from contracting blood diseases such as HIV/AIDS. If an addict chooses to use clean needles, good for them. In general though, most people looking for a high aren't really considering the consequences of sharing needles and exchanging them for new ones.