DEAR MISS MANNERS: My wife and I have a wide circle of friends and an active social life. The vast majority of our friends are very considerate guests and hosts. But we have one group of friends with a very relaxed approach to socializing. These friends will give noncommittal responses to invitations, accept invitations but cancel at the last minute, or arrive alone and state that their spouse could not make it. In our book, these were not friends worth having. We stopped issuing invitations to them and stopped accepting theirs to us. I thought that would be the end of it, until I encountered …