This kind of activity is an abuse of the free stock market system.
This activity does not generate wealth. It doesn't create something from nothing. And it doesn't add value to society. If they generated 21 billion, then 21 billion was necessarily lost by others.
People should look down on this kind of business and method of trading.
A common and understandable misconception.
For the remainder of this comment, I choose shares in Google as an example. I have no position in Google, not an opinion on their current price.
Both arbitrage (making use of inconsistencies in the market) and speculation (trading for immediate short term profit, and not for long term investment) are activities that add value. It is important to understand that markets are not only there to facilitates exchanges (e.g. trading in securities), but they also play a vital role in information processing. The activity of trading feeds information into the world: If a person buys 1 share of Google for the price of x, this person is also saying "I am willing to put my money on the notion that 1 share of Google is at least x". The current price of Google is nothing else than the consensus opinion of all market participants.
The accuracy and efficiency of said consensus depends heavily on the tools available to the speculators and arbiters. Say I think that Google is currently overpriced. If the market rewards me for supplying this information, then I would do it. For instance, I could sell Google shares short (i.e. I would sell shares that I don't have, hoping to buy them later on at a lower price and thus make a profit). At the beginning of the financial crisis, a lot of governments disallowed trading short, naively expecting the market to stabilize. What actually happened ofcourse is that information exchange slowed down: if Google was indeed overpriced, this would be known much later to the world if short trading wasn't possible.
The bottom line: speculation and arbiters bring their information into the market and are rewarded for this by their profits. If the information is incorrect, they will be punished with a loss.