I've often found ideals don't quite translate into practical application. Within economics, political theory, etc., I think TDD also deserves a place as a 'wonderful ideal' that fails simply because it does not take into account it's implementing process: human action. Not to mention that the way many programmers learn and code today seems at odds with the structured nature of creating tests.

Maybe there is a better approach to writing maintainable code than TDD? I imagine a world where all code is understandable, readable, and instantly recognizable, but once again we arrive at the fork where the 'ideal world' deviates from the real one in which we all reside. Shame.