"dirty"? I don't think so. To me it connotes a certain distance at which the relationship is maintained. Similar to having lunch with a co-worker (who happens t

"dirty"? I don't think so. To me it connotes a certain distance at which the relationship is maintained. Similar to having lunch with a co-worker (who happens to be the CEO) versus having lunch with the CEO. When you use business titles, it's a business relationship. When you don't, it's easier to be friendly acquaintances or even outright friends.