Thanks Dave, that might get me somewhere. The problem is not necessarily that the hair doesn't follow (it does) but that the follicle nodes don't update their transform channels. I don't actually need the hair, just a node that's locked to a spot on the cloth to which I can parent or constrain other stuff.

I'm mostly confused because the zipper tut I posted above clearly works this way, and now nParticles somehow have stopped behaving that way. If I create a bend deformer or otherwise deform the geo, the follicles do follow, just not with cloth.