However, they should have a "real investigation" to find out:
Why on earth did it rebound the way it did and remain stable the rest of the day ?
Why are their reports that traders were locked out their systems during the entire 10-15 minutes of the drop ?
What effects the "Working Group on Financial Markets" aka Plunge Protection Team have on the markets. This entity has absolutely no oversight and can pretty much manipulate the markets how it wishes. The "conspiracy theorist" in me think that they might have done this on purpose to send a message to certain Senators to drop support for the "Audit the Fed" Bill, which quite a few did shortly afterwards.
If it was caused by a typo, how can someone entering a "B"illion instead of a "M"illion cause this, normally wouldn't you have to enter 1,000,000,000 into the computer program instead of "Million" ? I guess unless they were using Microsoft Bob for Day Traders.
Anyway, that is my "Two Cents"
The UNIX philosophy basically involves giving you enough rope to hang yourself. And then a couple of feet more, just to be sure.