Might just be me, but with Google opening and closing invitations like this all the time, it's not even "like Gmail all over again". It's much worse. With Google creating this much artificial scarcity to bring buzz, demand and publicity, they are really creating immense expectations and putting themselves up for slaughter.
People are going crazy right now trying to get invites, to find the invites closed, their received invites not working because it's closed again, etc etc. People are putting up lots of work to get in, and the more work Google make people put in, the better the product needs to be.
The buzz around G+ is also just insane. People are creating news websites, tutorial websites and twitter-accounts for G+. People are gaming others to like and follow them on twitter and facebook(!) to get G+ invites (makes sense, eh?). There are already several third-party URL-shorteners dedicated for G+. Why exactly? If G+ is going to be huge, who cares about twitter's 140 char limit? The buzz-machine is working like crazy and people are desperately trying to cling on to what's hot right now, even though it doesn't internally or externally make any sense. Expectations are way high and are still going up, up trough the roof.
G+ seems 100% marketing-driven at this point, just look at the demo-material. In the Circles video they even say "You take a chance on people, because they take a chance on you". For a feature which lets you put a user in a list. This is Apple-grade marketing BS, so it's hard to not think the overall deployment strategy with the associated buzz is intentional.
I'm however starting to doubt if G+ will be able to deliver on the expectations being created for it. They are just going way too high now.
Although probably not as bad, this is definitely moving into Wave-land. People had to go trough hell and back to get Wave-invites, but they went trough whatever crazy means they had to, and once they got there the response was "This is it"?
Unless G+ can really deliver, it might end up the same.