The wilds are the untamed areas of the universe. They can be literal wilds like the Australian Outback, where there is little or no human civilization. They can be post-civilized type areas, which through any number of disasters from earthquakes to political collapse, have lost their former structure and security. They can also be areas of the mind and soul, such as the exploration of organized crime. Wilds merely need to be without definite boundaries or rules, and this can be achieved as easily through finding a frontier as in creating or re-creating a new frontier.
Truth be told, a story isn't even a story unless it uses some "wild" elements. Routine is not a story, but a deviation from routine is—pretty much by definition. After we are introduced to the characters in a story (ie: their routines), we are given the conflict, which drives the rest of the story. So I think it is also fair to say that all stories are mysteries, at least to the degree that you want to know how it ends. That being said, the greater the deviation and the more levels on which it deviates, the more compelling the story.
If something physical happens to a character (like an earthquake or an illness), he can still be ensconced in the routine of both mental and spiritual life. However, if the deviation is great enough to warrant the Great Question, why? then it has impacted the character on the spiritual level. It has called into question his belief system by challenging it. This is the reason that the wilds are important. Most people expect a certain behavior from the physical and political world, which is reenforced when catered to by media. Introducing the wilds is the act of opening these primary assumptions to questioning.
Without the wilds, no perspective can be gained by modern man on his spiritual and mental beliefs. He is merely trapped within his understanding of the physical world, which is limited to his proximity, and therefore a biased and limited perspective. I urge writers of fiction to take the hard road and shake spiritual foundations. I also urge you to do it with respect and fairness. Just go the extra mile and cover all the bases. You'll be glad you did.
Lost: The Complete Sixth And Final Season - This groundbreaking, epic TV series is based largely on philosophy and classic literature, but is told in a mysterious and thrilling style which is very contemporary. Its use of the wilds comes literally and figuratively. Not only do the characters crash on a mostly uninhabited island, but the island has mysterious powers. In my opinion, the most important thing ever aired on television.
FlashForward: Season One Pt.1 - This fledgeling show has many of the earmarkings that went on to make LOST great. Everyone in the world sees the future at the same time, the wild element is whether the visions will come true.