It's important to watch what trader/pundits like Jim Rogers actually do, not just listen to what he says. He's made a big deal about the current and future commodities boom, but he's also running a group of commodities funds. He makes bold claims about how Balliol MBAs should be buying farms instead of going into other industries, but he does not own any farms. He moved his young daughter to Singapore so that she could become fluent in Mandarin, he did not move her to Minnesota so that she could learn how to farm soybeans. It's always going to be better to be the commodities trader who controls a market than it is to be the producer of that commodity. If you watch what he has done, rather than what he says... you want to move to Singapore to broker commodities to the emerging asian markets, not move to Fresno to start an orchard.

Regarding "why" people may choose to make iPhone apps instead of farming. It's almost impossible to get started up in agriculture for someone who hasn't inherited a farm. Farmland where I'm from is over $10K per acre at the moment. You need millions of dollars just to buy the land. Then you need millions of dollars to buy all the equipment. Also, subsidies only happen for cash crops and commodities like milk and pork, you don't get subsidies for organic chicken and vegetables.