You mean legal and physical enforcement of the fact that you own the land? If people respect your ownership of land, that might be because: 1) they agree with the system that it is yours. 2) They fear the enforcement. This is the type of fear rjwood means?

In my opinion, ownership is definitely necessary for the various purposes i gave earlier.(except the one i edited to add) And it would be a virtue when the reason people respect it is the first one.
Perhaps this is a part of the justification of my leftish-ness is that if people are starving,(for instance) using resources that can be used to feed them, to make second houses can not really be respected by these people. How could we expect that from them. Maybe a better example is that you can not expect someone who works two jobs for his family to respect a pensioned rich dude with three cars sitting on his ass. They are effectively working to support that old guy.