????By Philip Elmer-DeWitt

????Pressure is mounting on Apple (AAPL) to do something about the netbook problem.

????IDC reported Friday that worldwide shipments of these sub-compact portable computers grew seven-fold year-over-year in the first quarter of 2009, according to Computerworld’s Agam Shah. By the end of the year, IDC estimates, netbook shipments could reach 22 million.

????Meanwhile, Apple’s market share is shrinking, and Mac sales fell last quarter for the first time in five and a half years.

????“Vendors are waking up to the fact that people respond to so-called ‘good-enough’ computing,” Jay Chou, research analyst at IDC, told Shah. “They don’t really need all the power of a Core 2 Duo CPU most of the time.”

????Steve Jobs famously dismissed netbooks as “a piece of junk,” a sentiment echoed two weeks ago by COO Tim Cook.

????“It’s not a space as it exists today that we are interested in,” Cook told analysts during Apple’s most recent earnings call. “Nor do we believe that customers in the long term would be interested in.”

????Apple watchers parsed those lines carefully, noting that “the space as it exists today” could change dramatically the moment Apple releases its long-awaited touchscreen tablet computer.

????But that misses the point.

????Netbooks, which sell for s little as $300 to $350, are typically used by students for note-taking or as light-weight secondary computers in situations where all one needs is a keyboard and a wireless Internet connection.

????An Apple tablet might be a game changer, but it’s not going to sell for $300. and it’s not going to serve those needs. Nor, for that matter, will an iPhone or an iPod touch — the devices Cook and Jobs have suggested are Apple’s versions of a netbook.

????That’s why the smart money is betting that Apple will respond to the growing netbook threat by cutting MacBook prices — sharply and soon — before back-to-school sales start, and parents who might have given their kids Apples for graduation settle for Acers instead.