Apple shares register biggest fall in four years

Apple Inc shares tumbled more than 6 percent on Wednesday, chalking up their biggest single-day loss in four years as fears grow about intensifying competition in the mobile device market.
Investors and analysts blamed the sell-off on a mix of factors, including a forecast by an influential research firm that the iPad maker is continuing to cede ground to rival Google Inc's Android gadgets, and unconfirmed reports that at least one major stock-clearing house was raising margin requirements on Apple stock trades.
Analysts also cited fears about a hike in the capital gains tax in 2013 in the event that ongoing Washington fiscal negotiations fail, as well as news that Nokia had beat Apple to the punch by striking a deal to sell its flagship Lumia through China Mobile, that country's largest wireless carrier.
Wednesday's drop rounded off a bleak 10 weeks for the most valuable U.S. company.
The stock was one of the day's biggest percentage losers on the S&P 500 , shedding $35 billion of market value as more than 37 million shares changed hands blowing past the company's average daily volume over 50 days of 21 million.
Apple's shares, once among the most desirable of portfolio holdings, have headed steadily lower since September on growing uncertainty about the company's ability to fend off unprecedented competition. This year saw a surge in sales of Amazon.com Inc's cheaper Kindle Fire and Microsoft Corp's first foray into the tablet market with its Surface.
Meanwhile, Samsung Electronics continues to chip away at the iPad's dominance with its Galaxy line.
The assault on Apple's consumer-electronics home turf presents a stiff challenge for CEO Tim Cook, who was elevated shortly before the death of Silicon Valley legend Steve Jobs and is now charged with keeping the world's largest technology company humming.
"This is not going to be a short-term trend. This is a management test, of how well they can perform without Steve Jobs," said Brian Battle, director of trading at Performance Trust Capital Partners in Chicago. Referring to Apple's new iPad mini, which is only a smaller version of the existing iPad, Battle said the company needs "another home run" for shares to return to levels around $700.