Please remember they are posessory rights, they dont have a title of property, i dont know how to express this in english, but here: http://en.wikipedia.org/wiki/Usucaption
I have long held to the theory that a properly functioning, legally sound, land registry and title deed system is the absolute foundation of a successful economy. And a major reason Anglo-Saxon economies have long outperformed most others. A vague claim on property is not worth risking money for.
that is why i am making it very clear. each should evaluate cost/benefit. Keep in mind that the same land with title of property is worth more than twice as much.