When a creative mind understands a system then that system becomes easy-to-use for purposes outside the imagination of the designer.
Example: A wiki markup will be overt when the formatted (and printed) output will suggest the input required to reproduce it.
Example: The maker movement asserts: you don't own it if you can't take it apart.
Example: One learned Smalltalk-80 by using the system, then typing ctrl-c (interrupt) to see how it did what it did.
Example: The Eclipse committer portal exposed its own functional test results, formatted, and indexed by every button presented to its users.
Counter examples include cellphone plans, set-back thermostats, wysiwyg editing of tables in word.
Wiki has turned out to be much more than I'd imagined! That is not to say that I didn't imagine a lot. These are the design principles I sought to satisfy with the first release of Wiki.