Margin trading for individual investors is a recent development. Previously, individual investors were not allowed to open margin accounts. As this old article explains, China brokerages became nervous of the margin debt at the peak. As soon as brokerages tightened margin requirements, the selloff began. This article from December 2014 goes into a little more detail on the recent history of margin in the China markets.
There is also Shadow debt in the market, off-balance-sheet debt invested in the market, sometimes at a leverage of 3 to 1. Normal margin accounts are much more restrictive, about 9%. This shadow debt has been around for a few years now, but the latest boom is much more recent.
It should be noted that the China market has had huge booms and busts in the past, without the more recent leverage.
I've always thought that a good essay writer can make a good programmer. In particular, good essay writers can make good programmer/analysts or project managers. In both worlds, you struggle with scope, organization, and fact finding. Answering the question "What is this paper/program really and truly about?" is the primary task.
I think this is more like an obsessive video game player, who plays the game enough to learn every trick and secret. For example, say there is a particular game boss you wish to defeat. Play enough, and you learn the boss encounter by heart. You will know what the boss will do and when. You will learn where to stand, what abilities to use, how to cheese it, everything. Eventually, you will be able to beat in your sleep. Is that hacking?
To me, hacking would be modifying the software or machine or obtaining the source code to find exploits.
This is stealing, like taking advantage from a malfunctioning ATM machine to obtain lots of cash is stealing. If you take money from a malfunctioning ATM, is that hacking? It is not.
This defeats the purpose of installing these types of systems. Instead of simply not knowing exactly what employees are spending their time on, they now have an inaccurate or down-right false picture of what employees are doing. This can lead the management to make the wrong decisions on things such as when to hire or how to allocate resources, especially when they believe the data over their lower level managers.
As I understand it, supposedly the market arrives at a price based on its perception of the value of the underlying company, with its future prospects and the time value of money factored in. Unless these algorithms are taking this data into account, I'm not sure this idea is true now. After all, these algorithms are the ones setting the price. If they are not looking at the underlying company while setting the price, then the price they set has nothing to do with the underlying company or its prospects. Of course, there are still trades made that take the fundamentals into account, but as more volume becomes algorithmic volume, then the relationship between the stock price and the underlying value of the company becomes more tenuous.