Abstract : What do you give for free to your competitor when you exhibit a product line? This paper addresses this question through several cases in which the discovery of trade secrets of a product line is possible and can lead to severe consequences. That is, we show that an outsider can understand the variability realization and gain either confidential business information or even some economical direct advantage. For instance, an attacker can identify hidden constraints and bypass the product line to get access to features or copyrighted data. This paper warns against possible naive mod-eling, implementation, and testing of variability leading to the existence of product lines that jeopardize their trade secrets. Our vision is that defensive methods and techniques should be developed to protect specifically variability – or at least further complicate the task of reverse engineering it.