PlayNoEvil has an interesting meditation up on some remarks made by Peter Edward, director of the Home platform for PS3, relating to some of their advertisers (Marlboro, Durex, and Bacardi - woo!), and tangentially, some of challenges of age verification and the threat of having to move and buy a new PS3 if your account is banned for not being able to play well with others (are we looking at another minor PR disaster when someone buys a refurbished PS3 that comes pre-banned?).
There was an implication that [banning by machine]is a much superior capability to other online services like Second Life. However, the PS3 has the advantage of being a hardware based system. Also, many online communities do support robust banning systems. Particularly, services that are targeted at children. Since the Playstation Network service is not a "for fee" service, identity and registration information could be weak. Also, banning is kind of a strange response for a service that seems to be focused on selling digitally distributed items (games, movies, music, etc.). It will be interesting to see how this plays out.
The gamesindustry.biz discussion with Edward that PlayNoEvil links to has the original snips on 'branding for mature users' and the 'you complain, we ban' system of policing they're intending on implementing.