Just read Do customers have responsibilities on Seth Godin’s blog. A sample quote from there:

It struck me that this would have been inconceivable for sober people just ten years ago.

Would it be okay for JetBlue to blacklist this couple? To say, “you guys totally crossed the line, you can’t fly with us any more?”

So this is kind of about turning clients away, if you like. It reminded me of a company that we do business with who similarly will turn away from clients and not do business with them if they don’t like them or they are not the right sort of client. It struck me then that this is also great marketing: if you do end up doing business with them then you are joining what you believe to be a more exclusive club and if you believe it to be exclusive you will try that much harder to join.

So this can kind of work both ways. Turning clients away makes for a happier business and .. more clients