Whether it's someone who's already in a relationship, a job for which we didn't make the shortlist, or an item we want that never seems to be in stock anywhere we look, human beings want the unobtainable -- that which is difficult (if not impossible) to make ours. Why does this happen? We assign a higher value to things and people that we deem as being in high demand. If something is too easy to snag, we're led to believe that no one else wants it, so we'd be settling for less by making it our choice. Is it any wonder that stores are able to lure customers with advertisements that say "available for a limited-time" and "while supplies last"? Are those products really in short supply? My guess would be no -- at least not all the time. Retailers capitalize on the fact that people have an aversion to feeling left out. The thought of someone else possessing an item they want for themselves drives people to shell out their money, often in la...