There are still some 'active' caches that were placed years ago and never found. 16 out of 62 caches in Russia were placed at least a year ago and never logged. This jem is from 2001 on the arctic coast.
http://www.geocaching.com/seek/cache...&log=&numlogs=
There is one on lake Baikal (the deepest lake in the world, holding 1/5 of all the worlds fresh water) that was placed in 2003, and after many DNF's, was found this summer for the first time.