In Clojure 1.3+, interned vars don't set the dynamic field in clojure.lang.Var and can't be used in a binding:

user=> (intern ns (with-meta 'dyna-var {:dynamic true}) 100)
user=> (binding [dyna-var "one hundred"] dyna-var)
;=> IllegalStateException Can't dynamically bind non-dynamic var: user/dyna-var clojure.lang.Var.pushThreadBindings (Var.java:339)

The var has the right metadata

user=> (meta #'dyna-var)
;=> {:ns #<Namespace user>, :name dyna-var, :dynamic true}

But doesn't set the dynamic flag on the var:

user=> (.isDynamic #'dyna-var)
;=> false

The push-thread-bindings function looks for the .dynamic flag. Vars created via def have it:

user=> (def ^:dynamic def-dyna-var 100)
user=> (.isDynamic #'def-dyna-var)
;=> true

Along with the metadata

user=> (meta #'def-dyna-var)
{:ns #<Namespace user>, :name def-dyna-var, :dynamic true, :line 6, :file "NO_SOURCE_PATH"}