While my wife and I were touring Bordeaux in 1988, we stopped at a well known winery for a tour. After the tour, we were in the tasting room. The owner of the winery was the author of a well known book on wine, which we had been using as a resource during our travels. We told the hostess that we were using the book and she asked my wife if we would like it autographed. My wife replied, "Why would we want that?". The author/owner was standing about 6 feet away. His French ego was definitely bruised.
While the following isn't really a faux pas, it was equally as embarassing for the victim. The company I helped found in the 1980s used the Unix operating system. In porting it to our computer we found a lot of bugs and fixed them. We missed this one.
When you wrote an e-mail on the system, it stored the text in a temporary file. Then when you sent the mail, it copied that text into all the recipient's mailboxes. If you had a large mail list and the system was busy, this could take a few minutes. One of our employees sent an e-mail to the entire company. After he hit send, he then sent one to his wife, which was full of cutsy, love-dovey kinds of things and hit send. What he, and we, didn't know was that the mail program used the same temporary file for each piece of mail that you sent. Therefore, he overwrote the first e-mail with the second while the system was still sending the first one to the company. Needless to say, there were chuckles coming from all over the building. Primarily from those whose e-mail addresses were at the bottom of the list. The bug was quickly fixed after that.