At the moment Google are testing its new Google+ project, invites have been sent out and according to Google “Already invited? We’ve temporarily exceeded our capacity. Please try again soon.” so even being invited is not enough you have to be fast too if you want to be involved. Google usually start off with a small group and then increase the numbers gradually until they reach the target goal, whatever that may be.
According to the Official Google Blog, they say;
You and over a billion others trust Google, and we don’t take this lightly. In fact, we’ve focused on the user for over a decade: liberating data, working for an open Internet, and respecting people’s freedom to be who they want to be. We realize, however, that Google+ is a different kind of project, requiring a different kind of focus—on you. That’s why we’re giving you more ways to stay private or go public; more meaningful choices around your friends and your data; and more ways to let us know how we’re doing. All across Google.
This is a chance for users of Google other tools to get in on the ground floor of new social networking scheme, it is all about connecting and while it may not grow as fast as Facebook, do Google really need that anyhow, they already have a huge userbase to work with.
Source [Google Blog]