The more I look at corporate social media (or conversational marketing) efforts (to use an umbrella term(s)), the more I think three things must happen: listen, acknowledge, demonstrate.
First: A company must listen to what its customers are saying. Whether that is within a branded social network constructed by the company itself or among the forest of social media tools that currently exists, it is a foundational skill.
Second: The listeners at the company should acknowledge what they hear. They can do this through engaging with the conversations via their own tools (blog, website, etc.) or by participating in the blogs, communities etc. where the conversations are taking place. It may be as simple as a "thank you for your advice".
Third: Companies must demonstrate that they have heard what their customers are saying. This means making changes to their practices, products and/or services if they need to. If you have introduced a new product based on customer advice, let them know! If you have changed the way your call center works, communicate this. And so on.
Many companies are already doing the first, and a growing number the second. I think a bare handful are doing the third. We have to beware here of a crisis of expectations. Once companies acknowledge they are listening, I think the clock has started ticking on a deadline: the proof that they did indeed, listen, is expected. If you don't demonstrate, you will destroy the goodwill you have so painstakingly created.
I twittered this quote from Heraclitus today, and am repeating here for your reading pleasure: "Those unmindful when they hear, for all they make of their intelligence, may be regarded as the walking dead."