Five is the magic number wrote:
It can't be the worst terrain in the nation, and the 40 starters limit is also a limit on how popular it can be - why don't someone start a competing event that can take 500 starters?
Part of Barkley's allure is in the small field, the cheap "entry" fee and the secrecy in how to even enter. I really don't think the RD gives a crap about making his event bigger. He wants people there who want to push their limits, mentally and physically, not someone checking it off a bucket list and only doing it to brag to their friends.
Having 500 starters is a logistical nightmare on any course even close to Barkley. You'd get a bunch of road runners trying to prove their worth and they would either get lost in the woods or get hurt falling over a rock/tree. They'd expect a medal, a shirt, water every 2 miles, timing clocks, chip timing, etc.