Google+ was to have surpassed 18 million users this week, according to new data analysis. The news came from Paul Allen, who uses statistics to track Google+ growth.

But the number of users is “only about 2.4% of Facebook's 750 million users,” notes BusinessInsider. The growth rate of Google+ is “certainly impressive,” BusinessInsider said.

But any Google product can be expected to get “millions of users from the get-go,” BusinessInsider adds.

In his blog, Allen said that over 750,000 people joined Google+ on Monday, which brought the total number of users to almost 18 million. In addition, there were two days last week when over 2 million users joined the service in a single day, Allen adds.

The number of users reached these levels without Google “marketing Google+ through any of its other channels yet,” Allen said.

Consider that over a billion people use Google products, such as its search engine, YouTube and Blogger, Allen points out.

“Chairman Eric Schmidt says the vision is to integrate circles and sharing with all the other Google properties,” Allen said in the blog. “When that happens, you will likely see millions of people joining Google+ every day for some period of time.”

Allen also wonders why Google has yet to start pushing the marketing of Google+.

“Perhaps the product management team is still trying to get the product right,” he speculates on his blog. “They are certainly paying attention to what customers are saying and responding quickly to try to improve the service. Perhaps the engineering team, which has publicly admitted some degree of surprise at the amount of traffic Google+ has already generated, needs more time for scalability. It's probably a combination of those two factors.”

In other company news, Google Ventures is doubling the amount it invests yearly to $200 million, according to TechZone360. Google Ventures is the venture capital arm of Google, Inc. – which means it potentially has a lot of resources behind it, TechZone360 adds.