By offering high leverage, the market maker encourages traders to trade extremely large positions. This increases the trading volume cleared by the market maker and increases his profits, but increases the risk that the trader will receive a margin call. While professional currency dealers (banks, hedge funds) never use more than 10:1 leverage, retail clients are generally offered leverage between 50:1 and 200:1, and even up to 400:1

Don't Deal With Anyone Who Won't Give You His Background
Plan to do a lot of checking of any information you receive to be sure that the company is and does exactly what it says.
Get the background of the persons running or promoting the company, if possible. Do not rely solely on oral statements or promises from the firm's employees. Ask for all information in written form.
If you cannot satisfy yourself that the persons with whom you are dealing are completely legitimate and above-board, the wisest course of action is to avoid trading foreign currencies through those companies.