If you want to share things with just your close family members, or just close friends, or just computer scientists... how do you do it? You create the respective lists. Initial problems.
- They will see the names of the groups and how you organized them (not good for "not so close friends", "hot girls" and the like).
- How do you find which pictures you've share with just a particular group of people?
But you also want to talk back and forth with them, wall style. You can restrict your wall to just certain lists, but you only have one wall... so you need a group for each list. Problems:
- They will see the name of the groups.
- Now you want to start a particular discussion with two lists, or with one list plus one person... create new group just for that?
- You have to go to your groups to look at your discussions with that particular groups, no overall view of your discriminated stream.
It is way to messy. Circles on the other hand, are not an afterthought. All your contacts are organized in circles, you share whatever you want with a particular circle, or any group of people you define on the fly. I still think the interface needs to improve a lot, and as well as the basic concept (we need at least sub-circles). But still, even as it is, it's already way better in terms of control of information.