At the end of the day, maybe all you need is your customer's e-mail address.
Which makes it even more important to encourage your winery visitors to sign up (read the comment thread).
A day or two after I wrote the two sentences above, I saw this comment over at Steve Heimoff's blog:
It is really shocking to me the number of wineries that make no effort to collect email addresses from tasting room visitors and, further, even those that do seldom use them! I was recently visiting a high end ($50-100/bottle) Sonoma County winery; purchased a couple of bottles, but no one even asked for an email address! Wouldn’t they like to sell me more wine? Are there really so many customers in this price range that they can afford this attitude?
Steve referenced the comment above in this post (item 3, "Wineries are starting to fall like dominoes"), and I was so amazed by it that I took the time to look up the original comment from Diane Thompson.