OH, I'm sorry you are feeling bad about this, Psyco1. It is admirable that you provided for your son's education, including advanced degrees. Perhaps your son and his wife chose to blend their names purely as a way of compromise. Many liberated women these days don't want to change their names when they marry....just a thought.
Other than the issue of the name change, how would you describe your relationship with you son? Do the two of you still communicate otherwise, see each other? If so, then you should not dwell on this, as it is wonderful to have a good relationship with our children.
patty