Apparently the exchanges are going to cancel some of the trades that happened during May 6th's selloff yesterday:

http://www.cnbc.com/id/37011368

http://www.reuters.com/article/idUSTRE6456QB20100507

http://www.foxbusiness.com/story/mar...lity-thursday/

http://www.nasdaqtrader.com/TraderNe...?id=ETA2010-30