
If I could own a single asset these days, it would be a premier sports team. Sports are one of the few things that people want to watch in real time which means that they will sit through advertising. If you own a team in one of the top leagues (NFL, MLB, NBA, English Premier League, etc) you have a monopoly on the best players, as long as you continue to pay them. Furthermore, players want to play against the best, so you have a built in network effect.
The only thing that can upset the apple cart, is if billionaire owners try to upset the network effect. They'd have to justify enormous salaries to the Lebron's of the world, but with merchandising, tv rights in a new continent, a huge ego boost and a strong euro, they're beginning to get to that point.
The NBA needs to follow Cuban's advice on players, but also needs to put franchises in Europe, and Asia too. That will keep the monopoly in tact and make these people buku bucks.