G+ is still in field trial, but it is far from "closed". I have 150 invites, as do all users to the best of my knowledge. The growth was limited for the first couple of weeks, but that is no longer the case.

I would disagree that controlled growth of a new product is a mistake for a company at Google's scale and brand recognition, and I would also disagree that it is still a "closed invitation-only beta thing".