The popular social media site, headquartered in San Francisco, allows readers to send and read tax-based messages of up to 140 characters.

FORBES: As Deficit Soars, Congress Suggests New Tax On Text Messages

The problem brought to light by the privacy organizations affects people with e-mail readers formatted in HTML, which includes popular programs such as MS Outlook, MS Outlook Express, Netscape Messenger, Eudora and Hotmail, according to the report, written by Richard Smith, a security consultant.

CNN: Privacy groups ask FTC to close e-mail loophole

Customers can also view the passages frequently highlighted by other Kindle readers to discover interesting and meaningful passages in books using Popular Highlights.

ENGADGET: Amazon announces $119 Kindle Paperwhite with illuminated, capacitive touch display

Most popular was World's 20 Richest People, which first captured readers' attention back in February.

FORBES: Most Popular Feature Stories Of 2004

They are a curious breed: trivia experts, steeped in popular culture (helpful for pun headlines, none of which Google gets), usually voracious readers, often unappreciated.

CNN: Why 'Amercia' needs copy editors

Though her novel had long been popular, the fictionally dystopian society Rand had written about long ago had in many ways become real, and readers wanted to understand better the picture drawn by this visionary.

FORBES: Book Review: Ayn Rand's "Free Market Revolution" by Yaron Brook and Don Watkins