Google gets close with its groups. But one thing missing, that would seriously limit mailing lists being harvested for unwanted e-mail, is giving registered users their own list addresses.
Sourceforge gives their users a sourceforge address. They also buffer their forum and developer services, so that it's hard for spammers to get user addresses and hard to abuse the addresses that they do find. That means that I can use their services rather freely without too much worry of drowning in a delusion of fake viagra offers and such.
The gmail accounts that Google sets up don't quite match. They are general addresses, and people tend to use them as such. What we want is for Google to provide group-only addresses, along the lines of