Facebook introduces chat sidebar

Facebook help center explains more about this change. As I see it, the change is about persistence. This encourages people to use facebook chat to talk to people more often. This means active facebook use. People are more likely to stay logged on to facebook (as opposed to logging out of facebook, people would just close the window or the tab) even when they are not using facebook. This is exactly what Eric Schmidt wanted people to do with Google. 

The one most important feature with this new chat is facebook's utilizing the power of data. Facebook knows who you are talking to most often and it prepopulates the sidebar with people that it thinks you are likely to want to talk to. 

Which friends appear in the sidebar? Can I add specific friends?

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.

sidebar options

Of course, you can search for anyone who is not on the list with the little textbox which starts searching the moment you start typing. (I can't believe people take incremental search for granted now that Google web search rolled out instant search. It was a such deal to me when I got it in Mozilla Firefox back in the bronze age.) 

The options gear box is there for you and is pretty much self-explanatory. 

It keeps what is familiar: green dot means available, gray moon means inactive, and no icon means not online (or appearing as not online). 

Facebook seems to understand that despite the proliferation of wide-screen devices, not every screen is in wide-screen format. It says the sidebar will only show up when facebook thinks it should. 

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.

Kyle is unavailable, but you can still send him a message. 

The notification stays on the screen briefly and then disappears. Also note the green dot on Kristin, who is online.