Fire the customer and make it snappy

I'm kind of fascinated by the concept of firing the customer. Seth Godin posts today about a couple that he wishes JetBlue would have fired long ago. While I think that firing the customer is something that is very serious and only to be used in extreme cases, we live in extreme times...

...what do you do if the customer abuses your staff?

...what do you do if the customer impacts the ability of your other customers to derive value from your products/services

...what if your customers costs more to serve than they deliver in profit with no additional upside like goodwill or brand enhancement

...what if your customer doesn't hold up their end of the bargain? I think about this specifically with regard to the type of work that I do; the quality of which is contingent upon having the customer *involved* in the process

...what if your customer is an evangelist, however one that the rest of your market finds unpalatable?

This is a timely topic for me as I work on a Service Level Agreement for the customers and partners of my team. But SLAs only work if you are part of the same micro system (where accountabilities can be identified and controlled). And customer need prioritization is a huge factor for us, and a challenge as we service teams across business units at Microsoft...whee!

What about the larger ecosystem? The external market? What about situations where you have resource constraints and want to focus on your "best" customers? How do you prioritize? How do you start to un-serve the others?