Twitter was left eating Instagram's dust after the photo-sharing site boasted that its community has breached the 400 million mark. Even more astonishing is more than 100 million of its users have joined only in the past nine months, according to Forbes.  

"When Instagram launched nearly five years ago, 400 million seemed like a distant dream. Now, we continue to strive to improve Instagram - helping you experience the world through images and connect with others through shared passions," the Facebook-acquired social media platform said in a statement. 

The significant increase in Instagram's users means that it will generate more revenue from advertising. It is estimated that its popularity will rake in as much around $1.5 billion ad revenue next year, and almost double that figure by 2017, according to Forbes.

The aim to expand advertisements has put the company head-to-head with Twitter, which is also pursuing an aggressive revenue-generation strategy.

Instagram is also quick to point out that 75 percent of its users live outside of the U.S., particularly from Brazil, Japan and Indonesia. This is widely seen to bolster Instagram's bid to expand its ad revenues as it targets overseas markets in Europe and Asia.

Instagram has also recently snagged celebrity users such as David Beckham and soccer player Toni Kroos, among other international stars that could further help attract more users due to their immense fan base. 

Collectively, the hundreds of millions of Instagram users have posted 40 billion photos at a rate of 80 million photos per day and clicking 3.5 billion likes, Wired reported.