⇨ Clojure on Heroku

Heroku explains why they have added Clojure support in addition to Ruby and node.js:

Ruby, Javascript, and Clojure are all general-purpose languages, but they each excel at certain use cases. Ruby's highly dynamic nature and emphasis on beauty makes it a natural fit for user-facing web apps. Node.js's evented concurrency makes it a great fit for the realtime web. Clojure covers a new use case on the Heroku platform: components which demand correctness, performance, composability; and optionally, access to the Java ecosystem.

The right tool for the right job.
More choice for the tool helps get the job done simpler and faster.