That's true as far as it goes, but there are plenty of other reasons it's become so prevalent. From a vendor's perspective: - Web apps often have a reduced su

That's true as far as it goes, but there are plenty of other reasons it's become so prevalent. From a vendor's perspective: - Web apps often have a reduced support burden relative to equivalent desktop apps because you have easier solutions for complete control over deployments: environments, live versions of software in play (often only one). - Subscription payment models are convenient for vendors: they can help smooth out revenue but, critically, can also increase lifetime value of customers. From the customer's perspective: - One less software system to deploy, manage, and support, - Managing backups is (should be!) taken care of for you, - Lower on premise hardware costs, - Your stuff is available from anywhere you have access to a browser, - Can enable frictionless collaborative working. With that said, it's arguable that a purely web-based SaaS model isn't necessarily a good fit: - The problem of lock in is often worse. Even if you have options to export your data, is it in a format that makes it easy to import into a competing offering? - Poor (or no) offline support, and unreliable operation with choppy connectivity. - TCO can be higher, despite reduction in on premise support costs. - Subscription payments can quickly mount up to death by a thousand cuts with respect to costs. - Your data is not only offsite, but may not be stored in the same country or even on the same continent: a deal-breaker in some scenarios. - Susceptibility to attack via DDoS, and other methods: at best service can be degraded or rendered unavailable, at worst your data can be compromised. SaaS is like anything else: it can work really well (Office 365[1], GitHub, GMail), or it can be decidedly ropey (Google Docs), or anywhere in between. [1] Within certain constraints - to me Office 365 still feels weak as a collaborative tool.