“Now that Apple Inc.’s (AAPL) market value has exceeded $500 billion, the biggest challenge for the maker of iPhones and iPad tablet computers may be staying there,” David Wilson reports for Bloomberg.

“Apple is the sixth U.S. company that has ever crossed the threshold, according to data compiled by Standard & Poor’s,” Wilson reports. “The others are Microsoft Corp. (MSFT), General Electric Co. (GE), Cisco Systems Inc. (CSCO), Intel Corp. and Exxon Mobil Corp. (XOM), in chronological order.”

Wilson reports, “All five companies were below $500 billion a year after reaching that pinnacle, according to data compiled by Bloomberg. GE was the only one to surpass that value afterward. ‘Getting there is hard,’ Howard Silverblatt, a New York-based senior index analyst at S&P, wrote yesterday in an e-mail. ‘Staying there is harder.'”

Read more in the full article here.

MacDailyNews Take: One big difference: All of the others were riding bubbles. Only Apple did it in the face of a worldwide recession.

Another big difference is the massive headroom Apple has for growth in personal computers, tablets, smartphones, and future markets (Apple TV/iTV).

[Thanks to MacDailyNews Reader “Aaron” for the heads up.]