What is written in the article is true for the major part,but the beginning of Futures and Options,and Commodities Futures,in my opinion,have made the whole scenario a bit different and similar to Gambling.
Now the most important thing is the expiry date of options and futures,and other things related with them.
The indices are liable to be manipulated in this scenario.The whole thing has become,a different ball game,with volatility taking over,in this Globalized times.
Hence,as of now, it is a daily affair as far as exploiting the market is concerned,but on a very very huge scale,than was the case,before!