Geoff Bobroff, a mutual-fund consultant based in East Greenwich, Rhode Island, said managers who bet heavily on Apple need to be aware that technology stocks, in particular, have been known to plummet. He cited Cisco, which lost almost 90 percent from its 2000 high to the 2002 low, Bloomberg data show.
"Now that the stock is approaching the stratosphere, you have to start thinking about what could happen if Apple hits a difficult patch," Bobroff said in a telephone interview.