No, G+ is already retarding FB growth, and just got 400million accounts.....the relevancy comes with the numbers which are growing faster than expected. Google displays G+ threads that appear in the top 10 of a search for users that are googling while logged into Gmail or whatever, and that is really helping the growth. The expectation was that G+ would reach 400 million accounts by the end of the year, but it did so earlier than expected.
Btw, Twitter had 140 million active users in march of this year.....Google just posted the stat of having 100 million active users ( and the total number of accounts, 400 million) , so it has a bit more to go to reach the status of twitter, but regardless, it seems doable now.
Google's recent announcement:
http://thenextweb.com/google/2012/09/17/as-predicted-google-passes-400m-registered-users-now-100m-monthly-active-users/
Twitter's active users as of March of this year (according to the Twitter folks)
http://blog.twitter.com/2012/03/twitter-turns-six.html
