it never occured to me that someone would be selling rvx to cover a margin call on other margined stocks.  They say that one will sell first their winners (rvx not likely given where the SP is), and then one will sell what is liquid...sell what you can...(without crushing the SP).  RVX is very thinly traded and therefore not very liquid at current price levels.  But I guess it is possible that things get so stressed that you would be selling rvx here.  I'd rather give up my left BRDT...
;)