Really? I think there are several take aways that will affect the markets for a while.
1) Prime brokers were blind to his exposure, using multiple prime brokers and also not having to report controlling interest in shares controlled by Swaps let one player control an amount of shares on single firms that no prime broker would ever let their clients control.
I'm fairly certain we'll see some overhaul on the swap side to shed more light on what positions they hold, similar to what hedge funds have to file quarterly.
2) Family offices have kind of slid under hte radar, hedge funds have to file quarterly docs on what they hold and report when they control more than 5 or 10%, depending on the jurisdiction. Family offices side step this requirement due to a quirk in securities law.
Again I expect this "loop hole" to be closed.
3) One firm essentially was responsible for most of the share price gain for a few individual stocks, specifically viacom where he bought almost all of viacoms share price appreciation. This bullying technique was common in the 80s bond markets due to the small number of players who could buy up bond positions to push them around. Those markets were reformed such that this doesn't really happen too often anymore. Bill, found a cunning way to do this in the securities markets.
The SEC is going to look at t his very closely, remember their mandate is to have orderly markets and this ordeal was anything but orderly.