Amusingly horrible question. Functional programming languages don't typically have class-based or prototype mechanisms, so why on earth would a named set of object interaction mechanisms be relevant - let alone displaceable?
I also think it is funny the status quo in language design is to effectively combine objects and functions but programmers and writers are not acknowledging this fusion. Ocaml, Javascript, F#, Scala, Ruby, Nemerle ... with varying ease, these languages all let you create lambdas, compose functions, functions as values. Even mainstream languages like C# and Java are awkwardly moving in this direction.
Scala does some crazy stuff to make "fusion" interesting. They allow objects in pattern matching by providing a specific mechanism for allowing an object to expose encapsulated behavior (extractors). Functions all belong to a parametric set of classes and have an "apply" method e.g. def add(x:Int,y:Int) = x+y is really Function2[Int,Int,Int]{ def apply(x:Int,y:Int):Int = x + y }. Likewise, any class or singleton object can invoked as a function by providing an "apply" method implementation.