http://www.ps3fanboy.com/2008/06/03/home-open-beta-to-be-similar-to-gmail/
So the open beta will be invite-only as current members invite new people to the service. If a healthy amount of invites are given to everybody I think this could be a good idea. GMAIL's initial rollout was a thing of beauty as people paid good money to find out what all the buzz was about. Obviously I don't expect people to do the same for Home but that's why I said a "healthy amount of invites". Doing it as an invite system should help garner interest so some people will check it out at least.
I'm still not entirely sold on Home but it'll be interesting to see how it shapes up.