As far as I know people won't be able to invite others, so there is no invite to share. You'll only be able to recommend (8) friends, and they will have priority on the others.
BTW: I am in the developer preview but I haven't received the invite for the real thing. I asked to the others in the sandbox but it doesn't look like there's any invite being received so far.
- They're sending 100.000 invites starting from today
- They'll ask some of the invited users to nominate others to also receive early invites
So they're probably not giving all of them away today, not everyone will get invites to share and if you do they won't be direct invites but nominations.
According to the Google Australia team, they won't be releasing the invites until tonight so that they will be up to handle the influx of users.
http://twitter.com/twephanie
Also, here's my email, if the nominations/invites exist: johngunderman[at]gmail.com Thanks :)
BTW: I am in the developer preview but I haven't received the invite for the real thing. I asked to the others in the sandbox but it doesn't look like there's any invite being received so far.