Google+ has become a social networking phenomenon and may very well surpass 10 million users by today's end and 20 million by the weekend, according to founder Paul Allen's new analysis.

Last night, Allen posted on Google+ the results of a “surname-based analysis”. It showed that “the number of Google+ users worldwide reached 7.3 million on July 10 — up from 1.7 million users on July 4. That is a 350% increase in six days.

“I am not claiming perfect accuracy, but I do think the model is sound,” Allen said.

Allen started with US Census Data about surname popularity in the U.S., and then compared it to the number of Google+ users with each surname. By using a sample of 100-200 surnames, he was able to accurately estimate the total percentage of the U.S. population that has signed up for Google+. Then he used that number and a calculated ratio of U.S. to non-U.S. users to generate the worldwide estimates.

Allen also mentions that if Google+ keeps its Invite button, it could hit the 20 million milestone by this weekend.

If Allen's right, then there is currently an average of more than one million new people signing up with Google+ every day since its June 28 launch.

In comparison, Facebook, which opened to the public in September 2006, had 30 million subscribers by March 2007 and now it has 750 million users. And in 2009, Facebook was gaining nearly a million new users a day, according to The New York Times.

What does Facebook think of the amazingly rapid growth of Google+'s users? Only Facebook knows.

Meanwhile, even though the current Google+ userbase still isn't close enough to the 750 million userbase on Facebook, it’s already impressive and is likely to give Facebook something to worry about.

However, Google+ hasn't officially released any information about the users’ amount.

We don't have any comment on the number of people in the Google+ Field Trial, a Google spokeswoman said.