Let me revise that slightly: the valid function is also potentially useful for people using mapMonotonic and similar "unsafe" functions, so I guess that one should remain.
For reasons I can't fathom, Data.Map exports the functions showTree,
showTreeWith, and valid, all of which seem to be intended for
debugging the map implementation. No user should ever need these
abstraction-smashing functions unless they're monkeying around with
mergeWithKey. If these functions are deprecated, they'll still be
available from the "internal" module Data.Map.Base. Data.Map.Base will
be exposed through Cabal at the request of Edward Kmett, although it
will remain hidden from Haddock and completely unsupported.
David