‘To smack of’ can also just mean to remind you of, to make you think of. It smacks of my East coast suburban youth. (It makes me think of something typical there) I don’t hear that word in Paris. To my ear, it smacks of Canadian French. (It sounds like something they might see) If you are using ‘smacks of’ to talk about a value judgment, it is used negatively. For example: To conservatives, the proposal smacked of communism and that was enough to ensure their opposition.

That's a really interesting question, Agustín. "Smacks of" I would say, suggesting a negative thing. Unless they're being sarcastic! Can you give me the full sentence and where you read it?

When something "smacks" you, it forces you to suddenly to take notice. Usually, things that _force_ you to take notice are negative, but not always. "Smack" is similar to "strike". However, since "strike" is less forceful than "smack", "strike" is used for positive as well as negative things. You could say "It struck me as odd that people were feeding the alligators." However, it is not merely "odd" to feed alligators. It is dangerous. "Strike" is not strong enough so you could say instead "The sheer insanity of feeding the alligators smacked of brainlessness." "Strike" is often used in a positive way: "It struck me that he had many talents". You couldn't use "smack" that way.

It's obviously used with positive things in that example, but it's normally used in connection with something negative. It sounds strange to use it with positive things.