I cannot believe that Anon would be foolish enough to pre-announce such an action, let alone actually conduct such an operation. The data structures
of the Stock Market have been heavily fortified/monitored against intrusion, (especially in the last decade). It would be a suicide attack, imo.
Such an attack would be considered, straight-away, as an act of Terrorism, and make the SONY outage look like college pranking.
Even more ominous would be a false-flag event done in Anon's name, to justify the controversial "Internet Policing" strategies that TPTB would love
to have working for them. The American Sheeple would give up , yet more, for the appearance of "security".
USCYBERCOM > Anonymous.
Wouldn't be surprised to see a "War on Information Security" in the future. 1984, much?