For Apple Inc. (NASDAQ:AAPL), it was the biggest loss in four years.
The Cupertino company's shares slid more than 6 percent on Wednesday as intensifying competition from other mobile companies raised concerns about it being able to maintain its market share.
Research firm International Data Corp also threw a scare into investors on Wednesday when it came out with a report which said that Apple would end the year 2012 with a loss in market share of its tablet devices at the expense of Google's mobile handsets.
According to IDC Apple's worldwide tablet market share will slip to 53.8 percent in 2012 from 56.3 percent in 2011, while Android products would increase their share to 42.7 percent from 39.8 percent.
The immediate fear stems from Nokia's Lumia 920 which has been recently launched in China in a tie-up with China Mobile, which is the country's largest network carrier. Apple has tied up with China Telecom and China Unicom but not with China Mobile.
There was another trigger in the sell-off in the stock as unconfirmed rumours spread that a major stock-clearing house was raising margin requirements on Apple stock trades.
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, Reuters reported on Thursday.
Apple's shares have been on a secular downtrend since September when its iPhone 5 was launched, but subsequent events and its own pessimistic forecasts of the sales of its iPads have dented sentiments.
The shares are still up a third this year but are down nearly 24 percent from its record high of $705.07, hit on Sept. 21. The stock slid more than 6.4 percent on Wednesday to close at $538.7923.