According to several online reports, Facebook's mobile apps for iPhone and Android appear to be changing users' address book entries to list their Facebook e-mail accounts instead of their previously recorded contact information.

CNET's Violet Blue notes that Adobe employee Rachel Luxemburg recently found that a co-worker's contact listing for her had replaced her work e-mail address with her Facebook e-mail address. "He discovered this only after sending work emails to the wrong address," Luxemburg writes in a blog post.

"When Facebook forced its hundreds of millions of users into an @facebook account, commenters across the Internet talked about alterations that had begun in their contacts and address books outside Facebook -- valid e-mail addresses were being changed for @Facebook without people's awareness or consent on their phones and computers," Blue writes.

Blue notes that similar reports have appeared at Hacker News, Slashdot, and Reddit, among other sites.

"Ideally, your smartphone's Facebook app would add information to an existing contact, not hijack it," writes Gizmodo's Sam Biddle. "And it's much harder to reverse, too -- if Facebook wiped out all of your friends' email addresses, tracking them down and entering them all over again would be a serious travail. There's an enormous difference between having an annoying email account you don't want put on your Facebook profile, and having that annoying email address permanently erase other email addresses."

"There are also reports of email messages disappearing entirely -- but Facebook tells us that such messages have probably ended up filed in the 'Other' category which becomes available when one clicks on 'Messages' at the left of one's Facebook home," writes The Register's Bill Ray. "That doesn't alter the fact that data on users' handsets (their friends' preferred email addresses) has been deleted without warning."

For now, Ray suggests, "it might be wise to remove the Facebook app for a while ... just until the situation becomes clear."