Don’t give people the ability to intuitively learn the system by filling the product up with hundreds of features, all designed to be quickly coded rather than intuitively used. Ensure that only the core development team of the CMS is fluent in using the system because of its complexity. (Wow, I sure hope that Nokia, Sony Ericcson et al like their phones, because no one else appreciates the features…)

Also, make sure the process of performing common tasks, like adding a new page (a news article, a new staff member) must be no easier than rarely performed tasks because you’ve been so busy learning PHP that concepts like Interaction Design have yet to be understood.

A demo is available here