Those of us who are trained cartographers and have been making maps professionally for years would like to see some way of setting ourselves apart from those who aren't. But can we really? Is it not just a gradient of professionalism?
I would contend that what sets any of us apart is:
1. The quality of our work.
2. The depth/diversity of our work.
3. The particular niches or areas of specialization that each of us might have.
Someone can have 20 degrees and certifications and have a body of work that is far from impressive. Another person could have a degree in Philosophy or Psychology and have some of the best, most functional/beautiful work on the planet.
What does certification give you/us that we do not have already? I suppose if folks are focused more on academia than commercial projects, certification might make more sense to gain better access to the certain journals or tenure or ???. However, when I am looking at other map designers and evaluating their work or looking for others to occasionally refer clients to, the first (and often ONLY) place I go is straight to their portfolio/gallery. It is cliche, but a picture IS worth 1,000 words!
If somebody sends me their resume and asks about an internship or gig with us, I'll spend 20-30 seconds skimming their written words, and 10-15+ minutes looking at? You guessed it: their portfolio/gallery.
I just don't see the purpose behind certification, nor do I care about "titles" or "labels." All I care about is that you can call me gainfully employed in the custom cartography business for the indefinite future.