[korny]

There are some big places using clojure - the Daily Mail uses clojure heavily for it's website, as do SoundCloud; also, like Scala, it's used internally at some financial institutions - CitiBank have some clojure, and we've been using clojure at IOOF (an Australian superannuation company).

Performance is probably the last thing you need to care about when choosing a programming language for most businesses - unless you are doing hard-core analytics or handling huge scale, you just won't hit the sort of performance problems that are solved by a faster programming language (as opposed to a faster algorithm or architecture).

It really frustrates me that people _still_ put such weight on low level performance. In 1997 I had people saying "don't use Java, it's performance is far worse than C++". It was mostly untrue for business problems then - and computers are many orders of magnitude faster now.

[puredanger]

Some other examples are Prismatic, Runa (recently bought by Staples), Climate Corporation (recently bought by Monsanto), Twitter (via acquisition of Backtype), etc. And there are a number of other big name companies very quietly using it to just get stuff done.

[epsylon]

As far as automated trading is concerned, performance is critical, which is why C++ still is king in this domain.