I've had this blog for a long time (April 2005, nearly 8 years). I'm sure I've written posts about why wineries should have a blog (in fact, the topic of my second post ever). I used to actually make regular posts about new winery blogs. I even have a category for blog posts on the topic of winery blogs.
Some wineries actually do have blogs, although the percentage is still miniscule in terms of the 6,000-odd US wineries. I'd like to think that such wineries are more successful as a result, but there's no data to support or deny that hope (since wineries are notoriously quiet about their actual sales and profits).
The fact is, most wineries don't blog. It's just surprising that more don't, notwithstanding Paul Mabray's belief that there are other things wineries should do first (with which I agree).
Anyway, I was reading my Twitter search results for "winery blog" (which is one method I used to keep track of new ones), and came across Why Every Winery Should Have A Blog which does a good job of beating the dead horse of winery blogging one more time.
Comments from wineries, both pro and con on the question of winery blogs, are welcome.