Leverage in trading is a good tool for those who use it properly. It is even better than good, it can be great. The people using it can be bad, due to inexperience or greed or otherwise - but don't blame leverage.
Once upon a time, when a trader wanted to buy $50k worth of XYZ shares, that transaction cost $50k. Today, the same transaction can be made for say $5k down as margin, and then $45k borrowed with a daily interest charge attached. This is leverage in action on stock trading, usually in the form of a CFD.
Prior to leverage becoming mainstream, when a forex speculator wanted to benefit from, for example, a falling NZ Dollar, they might have moved $100k of NZD into USD, with the expectation of NZD falling versus USD. If they were correct, they would later exchange that money from USD back to NZD with the expectation that it is now worth more than the original $100k originally exchanged. Today however with leverage, that same forex speculator can access 100:1 leverage on a trading account, meaning that only 1 per cent of the money needs to go down as margin, that's $1k down for a $100k forex transaction. This is leverage in action on forex trading.
The Bad Side of Leverage
Leverage gets a bad rap for a couple of reasons, mostly unfounded. One reason is that by the very nature of trading alone, the majority of people lose money and sometimes it is leverage that is blamed for this. However, an even larger percentage of small businesses fail, yet small business is still deemed ok. Most people who play sport, never make the professional money-making league. A large number of people not succeeding in trading to the highest level is a slightly silly reason to blame leverage for their misfortune. It is a tough game to win and a high performance endeavour. There is no field where everyone succeeds, trading is exactly the same.