This is exactly why I turned chat off. I have no desire to be contacted by old high school classmates who happen to be bored and browsing facebook, and see me pop up.
(Personally, I still feel surprised whenever I see anyone even using Facebook chat.)
With the old chat design, choose chat at the bottom right, then the "Friend lists" menu item in the chat window, and add the friends list you want to affect chat availability, and then turn availability on/off to particular lists.
Useful for parents and work colleagues who don't use other IM or who you don't want to give your personal IM accounts to.
I think its largest drawback was using account numbers, instead of allowing alphanumeric vanity names.
I don't know, was you the only person on that service and thus have no-one to talk to?
In short, Facebook likely contains everyone you've ever met or dealt with in person or online and "friended" that can potentially chat with you -- IM likely contains only the people you actually need to chat with.
"Everyone is there" is becoming an increasingly poor reason to justify selling your soul to a particular social network (as an individual or a business).
They've basically just brought facebook chat on par with instant messengers from the 2000s except you have to install something additional for video chat.
The parent is asking the equivalent of why you'd add maps to google when you have a perfectly good road map out in the car.
There are many people (including me) who have been using the internet for a very very very long time and don't see facebook as the internet even though we use it.
And I can see that I get quite a few sign-ups to my service that way.
Also the problem is not as much whether people use it for traffic generation. The problem is when they only use it for that.
I am actually beginning to consult my clients on how to build their own digital ecosystems so that they don't leave all the value inside the gates of facebook, twitter etc. but rather attempt to get the value transfered back inside their own ecosystem.
Once you start seeing it that way things start to look very different.
I made a longer argument about it here:
E.g. http://www.bell.ca/shopping/en_CA_ON.Unlimited-Social-Networ...
This kind of falls in line with my confusion as to why people ruin their websites with all these components and hooks into Facebook. They claim that they need Facebook Likes and Logins and Discussions in their websites, because Facebook drives traffic. Even if they hate it, they have to succumb to it. You know, for generating traffic. My question remains - why do you want to try appealing to a group of people to whom Facebook is "the internet" and who do everything through Facebook? Those people aren't going to make a point of going to your website again, unless someone links them to it a second time down the road. It seems like a lot of resources (not to mention website screen real-estate) given up for very little desirable return.