Historically, software vendors haven’t had to care too much about exactly how their software performed. Enterprise IT managers are all too familiar with the experience of buying commercial software packages and/or working with integrators in order to deliver software solutions that have turned out to consume far more hardware than was originally projected (and thus caused the overall project to cost more than anticipated). Indeed, many integrators simply don’t have anyone on hand that’s really a decent architect, and lack the experience on the operations side to accurately gauge what’s needed and how it should be configured in the first place.
Software vendors needed to fix performance issues so severe that they were making the software unusable, but they did not especially care whether a reasonably efficient piece of software was 10% or even 20% more efficient, and given how underutilize enterprise data centers typically are, enterprises didn’t necessarily care, either. It was cheaper and easier to simply throw hardware at the problem rather than to worry about either performance optimization in software, or proper hardware architecture and tuning.
Software as a service turns that equation around sharply, whether multi-tenant or hosted single-tenant. Now, the SaaS vendor is responsible for the operational costs, and therefore the SaaS vendor is incentivized to pay attention to performance, since it directly affects their own costs.
Since traditional ISVs are increasingly offering their software in a SaaS model (usually via a single-tenant hosted solution), this trend is good even for those who are running software in their own internal data centers — performance optimizations prioritized for the hosted side of the business should make their way into the main branch as well.
I am not, by the way, a believer that multi-tenant SaaS is inherently significantly superior to single-tenant, from a total cost of ownership, and total value of opportunity, perspective. Theoretically, with multi-tenancy, you can get better capacity utilization, lower operational costs, and so forth. But multi-tenant SaaS can be extremely expensive to develop. Furthermore, a retrofit of a single-tenant solution into a multi-tenant one is a software project burdened with both incredible risk and cost, in many cases, and it diverts resources that could otherwise be used to improve the software’s core value proposition. As a result, there is, and will continue to be, a significant market for infrastructure solutions that can help regular ISVs offer a SaaS model in a cost-effective way without having to significantly retool their software.