I'd like to bring this conversation back into consideration. I was looking over the realm lists and it occurred to me that at this time it is impossible for any new realms to form on either Dwilight or East Continent. In both gamer worlds the largest realm on the continent is too small to achieve the 15 player minimum. Ironically nearly half the realms on Dwilight and and over half of the realms on EC have fewer than 15 nobles, and EC features three realms with less than ten.
The supposed benefit of the 15 player limit that's been argued in this thread is that it prevents the formation of small, sparsely populated and uninteresting realms that are alienating to new players, but the idea of this benefit is unfounded. There is no evidence newly founded realms have a greater tendency to remain small, sparsely populated, uninteresting and alienating to new players. The newest realm on Dwilight, founded with only seven nobles is on the cusp of becoming the most populous.
It seems clear to me that a limit of 10 is much more reasonable than 15. I can tell you from experience a ten noble threshold will not make it easy to found a new realm by any stretch of the imagination. It will merely make it possible. Right now the limit of fifteen makes it functionally impossible to form a new realm on two game worlds (and I doubt the others are better off).
If the limit were scaled back to 10 I can say with absolute certainty that we will not see realms popping up all over until the noble populations of the game are dispersed to the four winds. In fact I doubt we will see a single new realm before the end of this year. So what possible reason remains for the limit remain at 15?
