On August 4, 2006 the eCBOT went down for 3 hours!! It sucked!! I had a short YM trade on. I covered as soon as the exchange came back up, fortunately, not as a loser. They said it had to do with "harmonization" of regulations. I remember thinking it was all about screwing the muppets like me!
In 87 was of the biggest problems was opening indices and you needed at least 80% weighting to be open. IBM was over 20% of the weighting. It was rarely on both Monday and Tuesday.