The authors range from prolific and best-selling author James Patterson to ex-Wonkette, Ana Marie Cox. Amazon will automatically show users blogs written by writers whose work they have purchased on Amazon. Visitors can also search for author blogs alphabetically.

Since its launch, Amazon has used community-building features, like reader reviews and recommendations, to boost purchases. "We always find that our users respond to content, which leads to better, more informed decisions and more purchases," said Amazon representative Christen Mariani.

Using viral marketing and blogs to sell books has already taken root among publishers and independent authors. "Within the past year we've started executing viral campaigns online," said Ashley Earnhardt-Aiken, director of marketing at Nelson Current. "We're also buying a lot more advertising on blogs either through BlogAds or Pajamas Media."

Earnhardt-Aiken said a successful viral campaign rests largely on the author, however. One Nelson Current author who recently benefited from strong viral marketing is Glenn Reynolds, a law professor who writes one of the most highly trafficked blogs on the Web, Instapundit.com. When Amazon recently began taking pre-orders for his book, "An Army of Davids," it skyrocketed from number 23,719 on Amazon's top sellers list to number 37 in a matter of days.

"We call him the 'Blogfather,'" said Earnhardt-Aiken. "All he had to do was mention the book."

Separately, Amazon.com said Thursday that fourth-quarter net income was $199 million, or 47 cents per share--compared with $346.7 million, or 82 cents per share, in the period one year prior. Sales rose 17 percent to $2.98 billion from $2.54 billion a year earlier, which missed analysts' targets of $3.08 billion. Amazon attributed the poor results to higher shipping and technology costs.

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