Well, there are a long list of requirements to reach Distinguished Toastmaster. The road is separated into two different Tracks, the Communication Track and the Leadership Track (the requirements for both tracks can be found using the links). You have to complete both tracks in order to reach DTM.
In the end, the DTM certification requires nearly 50 speeches, holding a position in Club and District Leadership, as well as completing something called the High Performance Leadership Project (details in the Leadership Track link), which is basically fulfilling the role of project manager for an event while working with an Event Committee and a Guidance Committee.
In this case, Toastmasters International actually follows well the C4 Principal (most likely without being aware of it). The organization has CONCEIVED a clear path for people to follow in order to improve their skills and reach goals. Not only is the concept COMMUNICATED well, but the whole organization is designed to improve your COMMUNICATION skills; as well as your COMMAND skills by introducing so many different leadership experiences, either as a club member, club officer, or district officer. Finally, Toastmasters International COMPLETES the process by offering evaluations nearly every time the member speaks, as well as in the way that the leadership positions are generally handled. When handled well, I doubt it could be any cleaner.
Thank you Toastmasters for providing me with the opportunity to polish my C4 skills, for providing a path for others to grow in these necessary attributes, and for providing an opportunity for me to meet and work with like minded people. I am proud to have the designation Distinguished Toastmaster, and I would encourage anyone who reads this to join a club. The time spent is worth it, and the benefits, greater than you can know.