telling the truth about wines

I recently spent an indulgent and thoroughly enjoyable evening in the home of some new friends. Like most of these evenings, there were numerous bottles of wine open and available for tasting/drinking. Out of the twenty something bottles that were open about half of them had been provided by the three vintners at the gathering - two comercial and one a dandy home winemaker. It's times like that when the "I wish I was a fly on the wall" comes into play. I noticed that all three vintners were watching the reactions to their own wines. Just how honest are people when they taste a wine that they know you made? What is most helpful to us? If you genuinely like/love it feel free to tell the person who made it just why you do - Conversely, if you really don't like it try to explain why. I backed against a wall and watched/listend while people tasted and observed that what is said when the wines are being poured blind is much more revealing than when those bottles are exposed and the vintner is standing there. When you don't like something it actually does help us if you tell us why. Sometimes it is simply a difference in likes and dislikes (I really don't like gamay) but sometimes it is something we are hearing that we really do take into consideration when making the next blends. There is no doubt that Gustavo makes wines differently now than he did 20 years ago and a big part of that is due to a change in when consumers are drinking the wines they buy. 20 years ago if someone bought a spendy wine it was going into the cellar. Now it is going to be opened within a few months. Does this compromise the winemaker or, over the years, does that palate also adjust because all of the other wines they are drinking are being crafted to drink at an earlier age?
For me any dinner with strangers always has an element of work attached to it because I am still watching/listening to their reactions to learn as much as I can. Great work if you can get it.