Several years ago, the only way to obtain an enterprise application was through a long, arduous and expensive system implementation of on-premise software--and oftentimes, after all the hard work, the project would still quietly be considered a failure.
Times--and, more importantly, technologies--have changed. Complex, on-premise implementations still exist, to be sure, but companies now have alternative options, thanks to software as a service, or SaaS.
Vendors in almost every tech category have moved into this delivery mode, either to provide an additional option for clients or to incorporate pre-existing systems in a hybrid strategy. Many vendors, of course, are pure-play providers, and have been since the beginning.
While the business case for SaaS is a compelling one--cheaper; easier to implement; automatic and more frequent application upgrades--it is by no means a foregone conclusion that it's best in every case.
Source: CRM Buyer, http://crmbuyer.com