Mesachek be-Kubia and Wall Street

According to this article, should Wall Street investors be disqualified from bearing testimony in Jewish courts? Read on...

Sanhedrin might be my favorite masechet. I've learned the whole thing through 4 times, and have had several other sedarim to learn various parts be-iyun, and am currently learning the first parts of Choshen Mishpat, which is heavily based in Sanhedrin. I've always found it to be a great mix of material. But I digress.

The third chapter of Sanhedrin deals with those who are disqualified to bear testimony, including relatives and those whose professions are 'shady'. Outright criminals are presumed by the Mishnah to be disqualified (for at least certain types of case, ayen sham), but there's another class who are considered to be rabinically disqualified.
One of those is the 'mesachek be-kubia' - the dice-player, the gambler. The Gemara records a dispute regarding the rationale for this disqualification - is it because they take money that the original owner really had no intent to part with (asmakhta lo kanya), or because they do not positively contribute to society (eino oseik be-yishuvo thel olam)? In other words, who is disqualified - the hustler or the gambler?

The practical difference between the rationales would be an occasional gambler - he participates in society with his day job, but then makes people part with their money on weekends. He's disqualified by the first rationale, but not by the second. Similarly, a particularly poor gambler, who only loses money, would be disqualified according to the latter, but not the former.
Practically speaking, the Rambam, and the Shulchan Arukh in his wake, ruled in accordance with the latter position, that oseik be-yishuvo shel olam determines the status of the potential witness.

A number of years ago, I asked the following question: what about someone who 'gambles' in a different way - a speculator, for instance. One could argue that investment - especially speculative investment - is what allows economies, and everything else in their wake, to develop. Investments were a bona fide contribution to society. Furthermore, investors often made money for others - perhaps if I gamble (and win) with other people's money, I'm oseik be-yishuvo shel olam because I'm not just in it for myself?
OK, then, so what about a day trader. His investments are very short-term - not helping to develop anything - are designed to be small enough not to create or upset trends, and is often done with one's own money. Perhaps such a person is truly not oseik be-yishuvo shel olam.

My thinking was largely theoretical, but I was reminded of it when reading this article. The description (caricature?) of the Wall Street investor in the article is very close to the mesachek be-kubya described by the Gemara the one who plays games of chance as a profession, and who engineers it so that he always comes out on top. It even fits with both rationales (asmakhta lo kanya has been taken to an entirely new dimension in the last year). So the question remains - if that NYT article describes what you do for a living, would you be fit to bear witness in a Jeiwhs court? If I was one of the judges, I'd have some serious doubts.

[Someone recently asked me for an example of something that I'm machmir on. There you go.]