> That's not really controversial or interesting. It is to me. So far it seems that everyone takes this for granted. I disagree: I have yet to see a problem cr

> That's not really controversial or interesting. It is to me. So far it seems that everyone takes this for granted. I disagree: I have yet to see a problem created by the "each class has an interface" rule, and I have seen countless problems created by classes without one. So: what problems are caused by interfaces with only one implementation?