Seth Godin talks about the responsibility of consumers to spread the word about both products, services and companies they like, and those they don't.
I found this interesting in relation to a discussion I was having with some family about the merits and demerits of Gossip. I am not sure whether it was Haidt in `The Happiness Hypothesis' or Gilbert in `Stumbling on Happiness' (both highly recommended) who was talking about the necessity of Gossip in a functioning society. Basically the argument is along the lines of, in a world where we don't know everyone and have personal relationships with everyone, we rely on Reciprocity (Reward and Revenge)and Reputation to make sure society functions.
It is counter-intuitive to say that Gossip is good. We gossip about people who gossip, and tell others how they are trust worthy. Trust is also good. Keeping Promises too. But... at what point is sharing information (which is always just a perception and never 100% confirmed truth) more important that just keeping your mouth shut.
Godin's argument in a commercial way is compelling. Obviously we can't all try every provider of goods and services. So obviously we should all participate in spreading the word about things we don't enjoy AND things we do enjoy.
It seems less obvious when it comes to personal relationships. After all, each interaction is unique... and everyone should be given a fresh start in every new interaction with every new person.