I again say "it's not a game" (really like the "how can it be a game when nobody wins?" comment above) but I found the most definitive proof that it should be a "sport": from http://www.geocaching.com/about/
Geocaching Resources
The Geocaching FAQ (Frequently Asked Questions)
Everything you would like to know about the Geocaching sport.
Celticwulf
nevermind - okay, here's my 2 cents: Geocaching is "Geocaching" it's not a sport, it's not a game but it is a game and a sport. Ultimately it is Geocaching.
Okay, problem solved...Next?