The concept of property, and the fact that our laws and government are built around protecting it, is the sole mechanism through which massive disparities in power are achieved and maintained in society. It centralizes wealth through avarice, making our stomachs unlimited in size. It also creates the dilemma of externalities, as we differentiate the value to us of the things we "own" versus the things we hold in common with others or that are "owned" by the state.
Property is also a entirely artificial concept. It takes the practical concept of use and possession and extends upon it to completely absurd extremes. It ties our society up in knots wasting a massive amount of human energy in the activity of determining and enforcing property ownership, and leads to incredibly convoluted structures in laws and markets, often leading to huge structural failures.
For instance, intellectual property law is completely absurd, on every level. It is an effort to force something that is fundamentally free and infinitely available to everyone to become scarce exclusively so that we can properly ensure it fits into a property-based system. The amount we lose as a society from the fact that all software is not simply open source is incalculable.