I decided to post this in a new thread in order not to derail becket's thread. There's a lot of good discussion there, by the way.
Groundspeak has received messages from The Nature Conservancy in Maine regarding geocaches placed on their lands without permission, and they have contacted individual cache owners in those cases where TNC has identified specific caches.
TNC generally does not allow geocaching on their lands, and they believe the lands are clearly marked. However, not all geocachers are aware of TNC's position on geocaching; hopefully the postings on this site will help get the word out to those who are new to the sport or are otherwise unaware that geocaches are prohibited there.
There are cases where specific permission has been granted such as TAT's cache at Mount Agamenticus. We would like to avoid further negative issues with TNC so they will remain willing to consider granting permission in exceptional cases. If you have a cache on TNC lands without permission, please disable the cache page and retrieve the physical cache as soon as possible. If you would like to seek obtaining permission for the cache, please disable it until permission is either granted or denied. If you have obtained permission, please note this in the cache description area on the cache page.
If you become aware of a cache on TNC lands, please post a "needs archived" note on the cache page as this will alert me to follow up to make sure the cache owner is aware of TNC's position.
Thank you for your cooperation.
-Brad / gpsfun