Is it primarily pension fund managers, or primarily mavericks and hedge fund 'activists'?
I'm thinking if it's the latter - too bad.
The former might be more of a problem, of course.
Even some goverments have gotten into the act.
But beyond this, I think that the increasingly consolidated clearing houses have become - unrecognised by most commentators - entities which constitute "single points of failure" undercapitalised for the risks that they actually run (as opposed to those they THINK they run).
IMHO, in the energy and/or metals markets at least, a "fat-tailed" market "discontinuity" is inevitable in the near future. "Any economic unit can emit money. The serious problem is to get it accepted" Hyman Minsky
