Facebook's new Sidebar Feature

Facebook has a new feature called The Sidebar. Some of you may have already bumped into it, while others haven't seen it yet. As usual, things like this are rolled out, meaning they release it to some people a bit at a time. Also, the Sidebar appearing depends on your screen size/space. If you have a widescreen monitor, you will most likely see the Sidebar sooner/more frequently.

I've checked it out and it seems useful and a good interface so far.

The sidebar is a new way to connect with friends you often connect with on FB. When it is open, it replaces the Friends on Chat list on the left.

from the help page:
The sidebar lets you quickly contact some of the friends you message most. Just clicking on a friend’s name opens a chat window. If your friend isn’t available to chat, you can still send messages for them to read later.

How you know a friend is available to chat:

Friends with a green dot next to their names are available to chat
Friends with a gray moon next to their names are available but inactive
Friends with no icon next to their names are unavailable

The sidebar is sensitive to the amount of free space you have on your screen, so it only appears if there’s enough room for it. If you don’t see the sidebar, just click Chat in the bottom right corner of your screen, which shows the same list of friends you’ll find in your sidebar.
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The list of friends in your sidebar is based on who you’ve interacted with most frequently or recently on Facebook. Since it updates dynamically, you can’t manually add friends to the list.

The list shows both friends who are available to chat and friends who aren’t. Clicking on a friend’s name opens a chat window. If your friend isn’t available to chat, you can still send messages for them to read later.
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To collapse the sidebar, select Hide Sidebar from the actions menu in the bottom right corner of the sidebar.

To expand the sidebar again, click Chat in the bottom right corner of your screen.

For more details:
Facebook Using the Sidebar
https://www.facebook.com/help/?page=194010440647624

Facebook Privacy for chat:
https://www.facebook.com/help/?faq=130254323719420