Yes it is part of BBM 5 and it allows each user to have a unique bar code design that is able to be scanned through the camera. When you want to add a friend or something, you would choose the scan contact option and position your camera over the bar code and it will automatically recognize and add the user.
Some people on crackberry have their "bar code" as their avatar and so you could just scan theirs by putting the camera right above that part on your screen. It will work anywhere as well. There is a poster for Tim burton's "9" at movie theatres. It has a giant bar code on it you can scan and it will take you to a site in the browser where you can view a sneak peek trailer.
But to answer the basics of your question, you can add anyone as long you scan their barcode. Anywhere the bar code is displayed it will be scanned.