While the rights of property owners are important, they're not absolute. It's prudent to recognize that there can be compelling (yet possibly competing) interests that require limits and restrictions to be placed on those rights.
As an example, say you own a piece of land. Someone else buys the land that completely surrounds it. What prevents the other landowner from fencing you in, effectively denying you access to and from the property that you own?
The only way to legally guarantee this doesn't happen is to limit the rights of the other owner (see http://en.wikipedia.org/wiki/Easement for more).
Some other limitations/examples:
The air rights over your land - aircraft are free to fly over your land without needing your explicit consent
Zoning and occupancy restrictions - you're not free to build a strip club in the middle of a suburban housing development
Safety of others - you're not free to booby trap the path to your front door, since that would foreseeably endanger people who are legally visiting your property (for instance, mailmen, public servants, and even pesky door-to-door salesmen)
This is not to say that all of these limitations are fair, or that every competing interest has merit. However, there are enough of these interests that many of these limits are codified into law.
[edited for readability]