It means that if anything were to happen with your product, you are on your own in fixing it. Every penny it costs to get fixed will come out of your pocket. By the time you pay to get it fixed, buy a new one or both, you will end up spending more money and certainly more time than if you had purchased a legitimate product in the first place.
Need proof? Call any of the companies directly and see what they say. They usually have it plastered all over their warranty page about unauthorized selling. Don’t be fooled into thinking they won’t know: they track every serial number on every product that is sent out and to whom it goes. When they see that it was purchased through a non-authorized form, the warranty is completely void.