By one estimate, Google + could hit 20 million users by the end of the weekend. (KAREN BLEIER/AFP/GETTY IMAGES)

That figure comes from founder and entrepreneur Paul Allen, who wrote on his Google + profile that his model for calculating the network’s size has found that the network has had a 350 percent increase in the last six days. He predicts that Google + could have 20 million users by the end of this coming weekend.

Allen admitted that his model isn’t perfect — he’s tracking growth based on U.S. surnames and then extrapolating from a ratio he made of U.S. to non-U.S. users — but thinks that it is pretty sound.

Google + users can now send invites to their friends, which means that network is likely going to keep growing at the same rate or faster.

Are you on Google +? How many invites have you sent?

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