Were I to design one, it would hinge on psychological warfare, the blackest of covert ops.
What used to work hasn't been working- at least two professional traders I know are adamant on that point.
It wouldn't be that difficult to design a black box that utilizes popular technical analysis patterns to confuse and trap traders. For all we know, developers use blogs to their advantage- there's a wealth of data in cyberspace.
If we're trading against a box that is able to intelligently predict our behavior given (historically reliable) trading setups, the box has the upper hand- especially if it's supported by vast amounts of trading capital that can be gambled as if it's OPM.
Is it possible that trading algorithms have simply become more sophisticated- while most of us are relying on outdated tools or outdated strategies? Worse, outdated concepts? 'What used to work isn't working.'
Just putting it out there for discussion.