I think Clojure is a good fit in a lot of SaaS applications, especially those that are complex. It helps in dealing with complex problem domains, and lets you reuse the same code on the client side (through the magic of ClojureScript). Small benefits accumulate, and while it's possible to write anything using any language and tools, Clojure reduces the amount of code and work that I have to do, thus enabling me to run a solo-founder business.