Your Facebook profile—and the amount of information available to others about you—is about to change considerably. Last year, Facebook introduced Timeline, a new kind of profile page that visually aggregates everything you’ve ever shared, liked or done on the social network and sites linked to it. Until now, using Timeline was optional. But, within the next few weeks, Facebook is making everyone switch over.

Once you are switched on, you have seven days to make changes to your Timeline before others can see it, giving you some time to hide posts from long ago that you may have forgotten about.

While Facebook users never like change, Timeline is arguably much more visually interesting than the old profile. That said, the new feature also raises some serious privacy concerns which I address in a bit.

How it works

First, you pick a photo in one of your albums (or upload a new one) to use as your “cover.” Appearing like a big banner above your profile picture, it’s the first thing people see when they visit your timeline. From there, you’ll notice everything is now in one place: the information you’ve included on your profile, your photos, everything you’ve ever “liked,” any Facebook apps you’re using, a map showing where you’ve been, as well as a timeline of everything you’ve ever posted.

You can add events to the timeline, as well. If you want, you can note everything that has ever happened to you from birth and add photos to create an online scrapbook to chronicle your entire life. To do that in Timeline, click on the “life event” option included in your status bar.

Timeline also posts activity from other Web sites and services that you use. So when you’re doing things like saving an image to your Pinterest account, or reading an article using the Washington Post Social Reader, the activity from each app gets grouped into its own box on your Timeline.

However, not all apps automatically post to Timeline. For some, you can turn on the "post to Timeline" feature right from the app install page. Others require you to do it from within your Facebook Account Settings, which you can get to by clicking on the small arrow on the very top right corner of your Facebook page. From there you can set the privacy of each app you’re using.

Facebook is currently promoting 80 apps that post to Timeline, including popular ones such as LivingSocial, RunKeeper, Spotify, TripAdvisor and Yahoo News.

Important Privacy Concerns

From now on, any events you add to your timeline default as public, meaning anyone on the Internet can see them. Public event posting created a huge problem for a 16-year old girl in Germany. So whenever you post something, make sure to specify who can see it, whether it’s all your friends or only certain people.

You’ll also want to check the visibility of past posts. Within your timeline you can go through each post that you'd rather not have visible and change the privacy setting, or change the privacy of all your past posts at once by going to Privacy Settings (which you can get to by clicking on the small arrow on the very top right corner of your Facebook page) where you can “Limit the Audience for Past Posts.”

And for both new and past posts, you can select the “Only Me” sharing option if it’s something you want to keep but don’t want others to see.

Location is another issue. While including geo-tagged photos and posts might not have seemed like a big deal when you shared them in your old linear stream, it’s a little different to have them all bunched together on a map, which is what Timeline now does. If you’d rather not have people seeing on a map the places you spend the most time, go back to each geo-tagged post and either change the location or hide it from your timeline.

Another worry is that hackers are going to try to lure disgruntled Facebook users to sites claiming to be able to switch their profiles back to the old look. Do not fall for this scam. If you do, criminals could get a hold of your personal information, hack your account and do all sorts of harmful things.

And many people are also concerned about the vast amount of data Facebook will be able to glean from its users. For example, the new feature that lets people add life events that weren’t posted on Facebook before actually is a guise to get more data out of you so advertisers can better target their ads.

It’s a pretty effective trick because if you’re not sure what kinds of events to add, Facebook will give you lots of suggestions. Here’s what I mean—when adding a life event you have to categorize it under various headings, such as work, family or home, and each one comes with several suggestions such as: new hobby, tattoo or piercing, new vehicle, broken bone and many others. It’s a pretty good lure to get you to engage with your timeline while Facebook gets a treasure trove of new data about you.

The issue is a hot one considering that Google is doing a similar thing. It recently said it is going to start combining the information it has on its users, under a new privacy policy that will become effective March 1. While Google already targets ads in Gmail based on what users write, it looks like the company will be using data it has about people in new ways. Not only does more data mean more targeted ads, The Wall Street Journal wonders, for example, if Google could notify you that you are late for a meeting because it can get your location from your Android phone and can see an appointment scheduled on your Google calendar.

If you’re bothered by such privacy concerns, check out our story on the many ways what you do online is tracked by big business.