I vote for some public wilderness. One of my favorite parts of any adventure is meeting someone along the way. Sometimes I'd rather not spend 20 minutes organizing a party. I still think private wildernesses are useful, especially when you don't want others camping all the mobs, but if we were to be given the option to enter a public wilderness, or a wilderness zone specially designed for public amusement I think it would be loads of fun! Respawn rates could be higher than normal, and I'd recommend a large map, even multiple connected zones of wilderness. We could have randomly generated bosses stroll through the zone occasionally (for the high level adventurers) and fill in the rest with appropriately leveled monsters depending upon the zone's recommended level. I want to see more than just 6 or 12 people out fighting monsters.
(Bosses should definitely drop chests!!)