David Fisher of What Is Noise has a must-read article on Customer Service via Social Media : "How NOT to handle Customer Service via Social Media". Shall you use Twitter or any other Web 2.0 tool to keep in touch with your customers, or shall you be still running an Enterprise 1.0 type of company, the 12 points listed are the very key requirements for any efficient/successful/committed Customer Care/Support/Service center.
Thanks to my own experience with building a such a service within the Optical Network Test division at Agilent Technologies *** years ago (hey, 1999-2000, that was even before the SMS became mainstream ;-), I would add a 13th one : Apologize even when that's your customer who's faulty. Because you're the one who brought the product to the customer.
thanks to Jean-Luc Raymond for the heads-up.