Facebook changed everyone's e-mail address without asking. Here's why.

Facebook has changed your e-mail address. At least that's how many felt after a quiet but vast change in the way the company displays users' contact information.

In yet another change to its website that irked users, Facebook replaced the e-mail address you picked to display on your profile page when you signed up for the online social network and changed it to an @facebook.com address.

Previously, users may have had a yahoo.com or gmail.com address displayed, so that if other users wanted to contact them outside of Facebook, they could. Sending an e-mail to a Facebook.com address will land the e-mail in the messages section of your Facebook profile. It means keeping Facebook's already-captive audience even more captive.

The e-mail change was first pointed out by bloggers over the weekend and publicized by media outlets Monday, leading to gripes from users, usually on their Facebook pages.

But you can reset your profile if you're bothered by the change. Facebook didn't delete the previously displayed e-mail addresses. To revert back to your original address, click on the "about" section of your profile. Once there, look for "Contact Info" and click on the edit icon on its right hand corner. There, you can change who can see your e-mail address and which e-mail addresses they can see.

Sending an e-mail to a Facebook.com e-mail address allows users to communicate with outside e-mail addresses via Facebook, but it's unclear how popular they have been. Popular as it has been with more than 900 million monthly users, Facebook messages and posts have not replaced e-mail, texting and other forms of communication.

Facebook didn't say why it made the e-mail switch, though it said in April it was "updating addresses on Facebook to make them more consistent across our site."

"Ever since the launch of Timeline, people have had the ability to control what posts they want to show or hide on their own timelines, and today we're extending that to other information they post, starting with the Facebook address," Facebook spokeswoman Jillian Stefanki said in an e-mail late Monday.

Facebook is well known for making changes to its website that have irritated users, sometimes temporarily. Some users are still holding out switching their old profile pages to the Timeline, which lists users' life events, updates and photos in chronological order, dating back to their birth if they shared that information on Facebook. In 2006, there was a big uproar over a now-central feature of Facebook, the news feed that tells people what their friends are doing.