The move is meant to help the site expand, but it risks undercutting one of its attractions: it has been more exclusive and somewhat more protected than MySpace, its larger and more freewheeling rival.
Under its new system, Facebook will create new networks for 500 geographic regions, and it will allow anyone to join them. In the default setting, people in the region — like the New York City area — will be able to see the full profile of other members in the same region. Facebook has long offered a series of options that allow users to expand or contract the information shown to various sorts of people.
I tend to think of openness not in terms of who can join, but what hurdles does one need to jump to access content. In those terms, Facebook is still a closed community and I think that tends to create an advantage for MySpace.