I don't see the purpose of having an empty mixin at the moment.  It's true that in the future there might be factored functionality.  Could you comment on this, do you already kind of know what common methods could live here?

Also regarding the API I'm wondering whether biclustering methods shouldn't be clustering methods too in the hierarchy; i.e. maybe SpectralBiclustering could be pluggable instead of K-Means by simply ignoring the column clusters, would this make any sense?