A few years ago, companies that needed highly specialized features would often opt for on-premise software with its attendant implementation and integration headaches instead of considering the relatively primitive on-demand offerings. SaaS has grown up, though--and the software as a service model allows a level of configurability that early on-demand adopters could only dream about. Indeed, "customization" stopped being an appropriate word a few years ago--at least for the SaaS environment. The word now really is configurability.
Source: CRM Buyer, http://crmbuyer.com