In today's unpredictable and dynamic environment, flexibility is an important aspect in system design. Flexibility increases system capability and effectiveness, reduces long term cost, encourages innovation, and protects against uncertainty. It is often at odds with optimization. High cost and harsh environment lead to specialized high performance satellite systems with stringent size, weight, and power constraints. These inflexible systems are costly to modify. The longevity of some satellite systems exacerbates the issue and leads to some existing satellites flying obsolete technologies developed more than 20 years ago. In this article, we argue that flexibility is a critical issue in satellite design. We illustrate flexibility through three example technologies; DVB-S2, SONET, and multiple-access receivers. The purpose of the examples and of this paper is to stimulate and encourage the community to incorporate flexibility in future satellite systems.