Well, in my last article about Google Plus, regarding their cute attempt to lure Facebook users disgruntled at the recent layout changes, I mentioned I was looking forward to hearing some of those early speculative numbers on growth. It turns out… I didn’t have to wait very long, because Ancestry.com founder Paul Allen is up to his statistical tricks again, claiming that Google Plus is exploding with growth since they opened the doors to the public earlier this week.

Google Plus Is Exploding

In fact, he says millions are joining the service every day, with as much as 30% growth in just the last two days. That’s insane.

On September 9, his estimate model had Google Plus at 28.7 million users. This morning, however, he says the site stood at 37.8 million users. He also uses a “fudge factor” to estimate private profiles and non-Roman alphabet profiles, which brings his total up to 43.4 million users.

From Allen’s Google Plus post sharing the estimates:

The timing on Google+ opening up to the public is interesting. Facebook has made a ton of UI changes this week and is holding it’s F8 Developers Conference today – in fact it is just staring now. According to a survey this week by Mashable, 72.2% of Facebook users hate the recent UI changes, including the News Feed redesign. Twitter’s stream was filled with complaints yesterday about Facebook under the hashtag #newfacebook.

Now, it’s important to point out that this is one man’s model–albeit a very, very smart man. Google themselves have not addressed the total number of users very much, so speculative math like Allen’s is all we really have to go on.

But even with a large margin of error, Allen’s numbers show a huge surge in sign-ups since Google Plus rolled out the red carpet to the general public.

Facebook is hoping to steal some of the spotlight back from Google Plus with their annual f8 event. For instance, they made a huge announcement today with Timeline, which will reportedly eventually become the default profile for users.

But 43 million users in a handful of months? And a lot of that coming in the last two days? I think it’s safe to say Google Plus is going to be around a while. It’s a long, long road to truly challenge Facebook’s dominance, but the growth of Google Plus has already exceeded what even some optimistic analysts predicted.

What about you? Are you one of them? Do you plan to be?