Clients will often want a service guarantee around features like speed, availability, support levels, data protection, and so on. Shortfalls will result in awarding credits, lost clients, or negative referrals, all of which impact the company. The IT systems and business processes will all have to support high levels of performance.
http://www.pcworld.com/businesscenter/article/142918/for_web_apps_get_a_service_guarantee.html