Hmm, I'm not sure that rule of thumb is very good. I think a better one would be "accept interfaces when you want polymorphism". Often I have a very high degree

Hmm, I'm not sure that rule of thumb is very good. I think a better one would be "accept interfaces when you want polymorphism". Often I have a very high degree of confidence that your caller will never want to pass a different implementation, and creating the extra interface for an improbably hypothetical situation just isn't worth my time? I'm not making any statements here, just wondering out loud.