There is, in fact, a continuum running from commercial banks to investment banks to hedge funds, and it is hard to see why some of this should be within the supervisory net and some without. This alone would argue for some degree of supervision - for example, limits on gearing - rather than just disclosure.
The case becomes stronger when we take into account the fact that the New York Fed has had to organise a support package for a large hedge fund on the grounds that its failure would have had systemic consequences (both nationally and internationally).