Landowner liability limitation
There are plenty of times the question of liability concerns crop up in the discussing placing caches. There is a real fear of getting sued in today's litigious society. Most, if not all, US State legislatures have enacted some form of "Recreation Use Statues." These generally involve protection of the landowner, relieves the landowner from the requirements to keep the land safe, does not allow the landowner to create a hazard, and makes it clear that the visitors must use due care when on the property.
Different states have differing laws and statutes. The below link goes to the National Park Service page that links to brochures for each state for further information: http://www.nps.gov/ncrc/programs/rtca/helpfultools/recusebrochures/index.htm
Each brochure has the title or code for the Recreational Use Statute for that state for further information.