[asynchrony]

Javascript strings are immutable and literals are almost certainly preallocated and stored in a table of constants. Why should using a string keys cause heap allocations?

[arohner]

If you have a VM where strings are immutable and interned, you're right. Java doesn't guarantee that strings are interned (though you can ask the VM to intern it), so Clojure treats them differently.

Also, Java declared java.lang.String as final, so Strings can't be extended to implement clojure interfaces to get nice behavior, like IFn and IKeywordLookup.