Drezner is skeptical of them:
The comparative advantage of smart sanctions is that they appear to solve several political problems for sender countries. Smart sanctions really do reduce the suffering by civilian populations. Because they are billed as minimizing humanitarian and human rights concerns, they receive only muted criticism from global civil society. Because they do not impede significant trade flows, smart sanctions can be imposed indefinitely with minimal cost. They clearly solve the political problem of "doing something" in the face of target state transgressions. What they don't do is solve the policy problem of coercing the target state into changing its policies.