That will be the number by end of today, according to FamilyLink founder and unofficial Google+ statistician Paul Allen. The number has grown from 90 million since Google CEO Larry Page's official statement just two weeks ago.
Allen's announcement comes as rival Facebook announces its public offering, and quite possibly the largest one ever. Not since Netscape's IPO at the dawn of the World Wide Web era has a tech company generated so much interest going public. But Facebook has a new rival that's growing fast and leveraging hard existing Google assets. By year's end, Google+ could have half as many users as Facebook does today.
"Google+ membership has grown more than 10 percent since January 19th when Larry Page announced 90 million users", Allen explains. "I have them at 100.8 million users by the end of the day".
Allen puts growth at 750,000 new users per day since January 19. He analyzes different surnames to calculate number of users. "If that rate holds steady, Google+ will end the year with 345 million users. But as I have said before, Google has many dials and levers to use this year to increase signups and usage, including its Android 4.0 rollout. I stand by my prediction of at least 400 million users by the end of 2012".
That's a big number likely to get a big boost just over the next few weeks. Last week, Google made two changes sure to open the floodgate of users: Allowing teens (rather than those 18 years or older) to join the service and permitting use of nicknames. Meanwhile, Google is connecting the social network to more of its services, including the new "Google Plus Your World".