Two of my favorite “bumper sticker philosophies” (i.e. short, pithy, and incredibly simplistic sayings) are “the simplest thing that could possibly work” and YAGNI. Avoiding unnecessary complexity and unneeded features are good ideas at first glance. The problem is determining what is unnecessary and unneeded. Just meeting the functional requirements is unlikely to be sufficient.
Read “Design? Security and Privacy? YAGNI” on the Iasa Global site for a post about how it’s important to have someone responsible for Quality of Service requirements in general and security in particular.