The worth-a-read new (free) white paper from VinTank on the state of wine industry social media answers the question thusly:
With all the activity that you need to do online do you really have the time to blog? We at VinTank believe in blogs, all types even winery blogs. However, with the limited amount of resources, with the amount of work it takes to build audience that differentiates you, and with all the other activities you need to do (e‐commerce, interact with customers, social networks, etc, etc) we feel that a winery blog is last on the list of marketing tactics (and we have been a loud opponent of winery blogs for some time). Approximately only about fifteen winery blogs even show up with traffic in Compete tools.
Moreover, we have heard consistently [from] blog readers complaining about infomercials and conversations about terroir, the weather, or a picnic that they had. If you do pursue a winery blog then commit to it. Find a voice or multiple voices at the winery that create interesting and meaningful content. And all the best of luck but send us your blog and we promise to add it to our RSS feeds and comment when we can.
In short, "Not unless you've got all your other marketing taken care of," which is equivalent to "No," since most wineries are chronically short of time and resources.