In a press conference today, Facebook CEO Mark Zuckerberg announced a major enhancement to Facebook’s messaging system that will allow users to send or receive messages from Facebook via traditional email accounts. But what does the announcement mean for user privacy?

Before tackling the privacy question, here are some more details on the new “Facebook e-mail.” First off, it’s not e-mail, or at least Facebook isn’t calling it e-mail. Rather, as explained by Facebook spokeswoman Meredith Chin in this USA Today report, “People are given the choice to opt in to having a Facebook email address as a way to have one destination for all of their messages. But, this product is not email. It is modeled much more after Chat.”

An official Facebook blog post also takes the “it’s not e-mail” stance:

You decide how you want to talk to your friends: via SMS, chat, email or Messages. They will receive your message through whatever medium or device is convenient for them, and you can both have a conversation in real time. You shouldn’t have to remember who prefers IM over email or worry about which technology to use. Simply choose their name and type a message.

We are also providing an @facebook.com email address to every person on Facebook who wants one. Now people can share with friends over email, whether they’re on Facebook or not. To be clear, Messages is not email. There are no subject lines, no cc, no bcc, and you can send a message by hitting the Enter key. We modeled it more closely to chat and reduced the number of things you need to do to send a message. We wanted to make this more like a conversation.

Facebook is rolling out the service to only a few thousand users at first, but plans to offer the service to all Facebook users in the coming months.

Perhaps predicting that there would be concerns over privacy, Facebook has been proactive in stating that the enhanced Facebook messaging system does still allow for customized privacy settings. Using privacy controls, Facebook users can choose who is allowed to send them messages. Facebook also promises that it will crack down hard on spammers and that developers will be unable to contact users without their permission.

But wait, there’s more…

Though these are admirable steps, there are still other privacy questions. For instance, how does advertising fit into the new messaging system? In this case, Facebook’s message system is like traditional e-mail. Just like Google serves up ads in Gmail based on the content of your e-mails, Facebook will serve up ads based on the content of your messages.

Another question is how far back do the messages go? Going back to the Facebook blog post, we see Joel Seligstein write,

“I’m intensely jealous of the next generation who will have something like Facebook for their whole lives. They will have the conversational history with the people in their lives all the way back to the beginning: From ‘hey nice to meet you’ to ‘do you want to get coffee sometime’ to ‘our kids have soccer practice at 6 pm tonight.’ That’s a really cool idea.”

Thankfully, Facebook allows users to delete conversations, negating the “coolness” of this feature, but the question of how long the conversations remain on the Facebook servers is still (as far as we can tell) unanswered.

Bottom line: Facebook’s announcement means that the way we choose to share information and interact with one another online will be even more important in shaping our offline reputations. Whether you’re texting, chatting, or e-mailing, whatever content you share needs to be fully vetted before it hits the web. Don’t let an errant message rob you of your good name online.

Here’s a Fact Sheet from Facebook explaining more details about the specifics of the new messaging system: