Quote from dbTrader:
When you sell a covered option (call or put) you will guarantee income from the premium versus the possibility of a large capital gain. However, the only way to hedge your underlying position regardless of market movement is to buy an opposing option. So, while there is no such thing as a free ride here - the cost of the opposing option will either take up some, all or exceed the premium received.
In the case of a downtrending market, selling a covered put will bring in more income than the premium to purchase a call option to cover an upswing. The only problem is that the small investor
probably doesn't have the capital to make this spread worthwhile so he/she usually leaves the weak side open, bearing the risk. This is why brokers require that you read about the risks, so you can't come back and say that they let you do something that caused you huge losses that you didn't understand.