@rq Hm~ I would expect that short-input hash functions are useful for key derivation (not from low entropy something, but when you have key K and want to generate various keys from K that are "unrelated" to anyone who doesn't know K; there's a more specific name for it and a contract-and-expand construction that does that that has an rfc that i can't recall the name of right now).
@rq Ah, I'm being silly: there, a MAC is sufficient.