Until now, Google+ had only been available to people who received invitations from existing users or Google employees.
In what is set to be a social network battle, Google+ is by far the search company's most ambitious product in its attempt to challenge Facebook's unrivaled popularity and success.
Launched in late June, Google+ has already garnered 25 million members and expects to reach 100 million users by the end of 2011. In contrast, it took Facebook 10 months to reach 1 million users in 2004. Facebook, however, already has 750 million users, with a staggering 1 trillion hits per month.
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The launch was also celebrated on Google's main search page, with a special blue arrow doodle pointing to the new "+You" button which links users to the Google+ page.
What is Google+?