I don't think you understand Clojure as well as you think you do. Java libraries often expect interfaces to be passed in as a parameter, and Clojure proxies are just a way of generating anonymous interfaces. This is not the de facto method for Java interop, it's just a simple means of creating the IFactoryFactory behemoths that Java tends to expect. It's practical, clean, and useful. I honestly don't understand what the nature of your objection is.