Shares of AT&T Inc. (NYSE: T) had their biggest decline in more than 5 years after the largest phone company warned of "softness" in its consumer business and that more of its customers have had their service disconnected for failing to pay their bills.

In late afternoon trading, the exclusive seller of the iPhone, was down $3.51, or 8.6%, to $37.52. The company's mobile phone and corporate business has not been hurt by the slowdown, Bloomberg News quotes Chief Executive Randall Stephenson as saying.

Shares of AT&T have jumped 12% over the past year. This year, though, the picture is different. The Nasdaq Composite Index has plunged about 8% in the early days of 2008 amid declines by stalwarts such as Google Inc. (NASDAQ: GOOG), Apple, Inc. (NASDAQ: AAPL) and Microsoft Corporation (NASDAQ: MSFT). AT&T has dropped almost 9%. The tech index hasn't had a positive day yet this year.

What's going on here? I don't think it can all be profit taking. Investors seem to be concerned that the slowdown in consumer spending will hit corporations as well. That won't be clear for another few months. It certainly kills some of the buzz from the Consumer Electronics Show.