The idea of this cache is to encourage people to visit neglected caches.Basically, you can only count the caches that have been neglected for 6-months or more. Take the number of days between the last visits and yours. Add them together to equal 5 years, 10 years, etc.
It's caused quite a flurry of cachers seeking out the "Forgotten", with people crowing victory on the Southeastern Michigan Geocaching Group's FB page. There's a neat little macro for GSAK to help them out. I qualified awhile ago, but TaGeez needed a few more. We had two victories this weekend!
WDC - Phone a Friend GC1C3ZA was 13 months unfound!
and WDC - E-Z Projection GC2DKBY unfound 15 months!
One more find and TaGeez can claim all 6 challenges! Woot!