A lot of wineries cite concern about the possibility of negative comments when asked why they are reluctant about using social media like Twitter and Facebook.
Here's a company in an industry which is easy to hate (insurance) that let's it all hang out on their Facebook page: Esurance. The comments are unmoderated, so you see complaints with praise. There are two things that make this page work in favor of Esurance: they actively participate in responding to customer comments, and they seem to care.
And yes, this takes time and effort on their part. Social media benefits are not free, or even cheap.
Social media for wineries takes balls.
Esurance commerical which talks about their Facebook presence (they're "in a relationship"):
Article: Hitch Your Boat to Customer Advocacy (also mentions failed Twitter campaigns from McDonald's and RIM)