Why trader is banned?

some time ago I was chatting with some people around my house, I talked about trading or currency trading is precisely the market through the internet and of course, traders are required to at least know the procedure for computer usage. From several conversations which were related to legal issues trading itself, it is said there are some scholars who are mengdibolehkankan and there is also a mengdilarangkan. Why banned? Trader is a business that can be said to be invisible and many risks, many do not believe about trading work, imagine in a few seconds, a trader can suddenly rich, or poor by a sudden as it is very necessary in-depth understanding of trading, do not know if this is categorized as pemahan trading is prohibited, because if trading is like gambling game wheel that we do not know where the cessation of the needle wheel. Why Allowed? As the above explanation about why trading is prohibited, permitted there is any related reasons, trading based on perfect knowledge, ranging from understanding the operation of computers, capable of understanding the trading analysis, and understanding the existence of a trading profit and loss, and most important is the way trading is not then this is where the greedy dibolehkankan trading position. Permissible and the forbidden is to be maintained for the sustainability of results blessing for traders. If we assume that the trader is prohibited then inevitably have to be abandoned, but on the contrary, if trading is considered permissible then that is a working farm or business that is quickly making a profit for a trader or otherwise.