by Ben Parr (MASHABLE)

The rise of Twitter has been the talk of the tech and media world. Last year, it grew 422%. That’s staggering, but nothing compared to the 1,382% growth it experienced earlier this year. And that was before Ashton Kutcher vs. CNN and mass celebrity adoption.

Its growth probably played a big part in Twitter’s recent $1 billion valuation via a staggering $100 million investment. However, an analysis from web stats firm Hitwise may indicate that this investment was a bad idea, as the numbers indicate that Twitter () has hit a growth ceiling.

Will Twitter Restart Its Growth?

The analysis, by Hitwise Global Research GM Bill Tancer, first graphs out marketshare of U.S. visits to Twitter, as compared to all other websites. In September of last year, it was around 0.01%. Then growth skyrocketed to a high of around 0.20% in June 2009. Since then though, it’s been dropping, and is now at 0.17%:
The graph of search volume for Twitter tells the same story. Over 0.06% of searches were for Twitter in July, but has now dropped to 0.053%.
Hitwise’s theory is that new user adoption has hit a resistance point. It provides data showing that there has been a significant drop-off of new users to Twitter from the world’s most popular website.

We’ve noticed that Twitter’s phenomenal growth has been stalling, but so have most social media sites this summer. The question is whether this trend continues into the fall or if Twitter can kickstart new user adoption with new features and new influx of cash.

Our opinion? The biggest challenge Twitter faces is finding ways to stop new Twitter users from quitting. It may even be the microblogging service’s Achilles Heel. But they have a seasoned team that’s growing rapidly. And now, with its new cash infusion, it has the ability to acquire new technology and talent to solve this problem. We hope and expect Twitter to get back to its growing ways.

But what do you think? Is Twitter done growing or is this just a bump in the road? Let the debate begin.