As expected, Google+ keep its Invite button available to grow the number of users in Google+, as a result, the number of users has crossed 7 million mark on July 10. The number of users are rapidly increasing and it is expected that the number of users will increase to 10 million today (July 11). The number of users reported on 4th July as 1.7 M, its growth percent is marked at 350% in six days.
Google+ will easily reach 20 million user milestone if the keep available the invite button for the users. Facebook is been worried about this increasing growth rate of Google+, and is updating its UI and introducing new feature in very hurry, It may be good or bad (that the time will tell). But this growth will surely satisfy the hard work of the Google+ Engg.