I really enjoyed reading this post from Underwood Wines, which sums up very well how the wine trade (and other industries) are making good use of social media, without it really being a particularly quantifiable medium in terms of measuring its business benefits. Social media definitely has a benefit, but just try measuring it!
Have a read - it's a great article, and while you're about it you can sponsor Todd and the team at Underwoods in raising funds for their local Air Ambulance service.