As opposed to the more traditional brokers, the new bonus structure offered by CySec-licensed brokers includes a trading requirement which if met, can be withdrawn.
Bonuses lay at the core business model of the new CySec-licensed brokers because it allows them to compete more effectively on one hand by creating a set of incentives unfamiliar to brokers like Morgan-Stanley, or Dean Witter, while at the same time act as a risk management tool creating a cosmetic buffer between winning trades and funds approved withdrawals.
Different brokers will have different requirements for cashing out. For instance, Cedar Finance requires you trade the bonus 40 times before you cash out, while Redwood will require you trade it 30 times before withdrawing your money.
Generally speaking, the bigger the bonus the higher the trading requirements.
There are also cash back bonuses that are offered on losing trades. Some will give you up to 50% back in the form of bonus currency if you consistently lose.
At the end of the day, the more you deposit the better terms you can get for your investment. Just remember to do your research read some broker reviews before investing.