Bacteria, viruses, mutant fungi, all these microscopic possibilities for altering brain chemistry. I feel like a mad-scientist from a hundred years ago, but using microbes in place of electricity and magnetism.
Still, I can't help wonder what would happen if a virus altered our brain chemistry (because every SF reader knows that would automatically trigger very precise behavioural change -- haha) and suddenly we only felt possessive about objects we were touching. Lose physical contact, and we know longer feel a connection to the object.
How would altered emotional attachment affect the economics of our world? Would our houses become smaller, having less to store? Would how we define love alter? our relationship commitments? And if possessions help create our identity, who would we be? where would our passions find root?