I first learned about boogers when I was geocaching in Orange County. I went looking for a "booger" near work, and didn't know what to expect. When I got to the GZ, I saw this green thing, otherwise known as a public utility box, and found the cache. There are at least two challenges that require finding a number of these caches, I know of, one in Orange County - Picking Boogers Challenge, and one in Santa Barbara - The Green Power Box Challenge. The one in Santa Barbara also requires finding a number of gators, which is another nickname for these units.
*****Congratulations to w01f for FTF 
*****
Happy Caching! A cache a day keeps the doctor away
Feedback is always appreciated on the difficulty/terrain ratings, cache descriptions, etc - thanks.