massive Chinese factories with below-average suicide rates
Wait... that doesn't seem to fit. Or maybe you're saying that keeping Chinese workers alive is a problem. In which case, you've got a point...
What if the answer is an overly active sex life and a lack of commitment to one particular women?
Obviously, the only reason this was modded funny was the ridiculousness of the suggestion that anyone on slashdot could possibly have a sex life, let alone an overly active one.
And then you have the wall street leeches who juggle numbers around and suck millions out of... what exactly? The world is not richer for them in any material sense.
This is at least theoretically untrue. The idea behind investment in general is to control the flow of capital to allow "the people that actually produce stuff" to work as efficiently as possible and to produce the stuff that society wants the most. As previous posts have stated, the supposed social benefit of this specific high-speed trading is to increase liquidity and thus increase the ability of investing to carry out its purpose.
Now, how that actually works out the in real world can be debated, and there is good evidence for both sides (quantative finance being good for society or quantative finance being bad for society). But there is at least a theoretical argument (and a lot more than a theoretical argument) that they DO make the world richer in a material sense.
If it's worth doing, it's worth doing for money.