The service allows users to take photographs, apply a range of visual effects and share them through Instagram itself or other social networks, including Facebook and Twitter. The most popular technique is to give photographs a retro feel, as if they had been taken on a Polaroid instant camera.
Kevin Systrom, chief executive of Instagram, which was founded less than two years ago and has just ten employees, promised in a post on the company's blog that the service would continue in its current guise rather than becoming just another Facebook feature:
"It’s important to be clear that Instagram is not going away. We’ll be working with Facebook to evolve Instagram and build the network. We’ll continue to add new features to the product and find new ways to create a better mobile photos experience.
"The Instagram app will still be the same one you know and love. You’ll still have all the same people you follow and that follow you.You’ll still be able to share to other social networks. And you’ll still have all the other features that make the app so fun and unique."
Despite those reassurances several users reluctant to remain a member of a Facebook-owned service had, within hours of the announcement, posted how-to guides for exporting their archive of images and closing their accounts.
Mark Zuckerberg, Facebook's chief executive, used his own website to announce the deal and reiterated that it would be business as usual for Instagram's 30m users:
"We need to be mindful about keeping and building on Instagram's strengths and features rather than just trying to integrate everything into Facebook," he wrote in a post on his own Facebook profile.
"We plan on keeping features like the ability to post to other social networks, the ability to not share your Instagrams on Facebook if you want, and the ability to have followers and follow people separately from your friends on Facebook."
The purchase will be funded by cash and shares and is the first of its size for Facebook. Zuckerberg ruled out any more acquisitions on the same scale in a statement this afternoon: "We don't plan on doing many more of these, if any at all."
The enormous size of the Instagram deal is likely to spark debate as to whether a second tech bubble is on the horizon. Facebook itself is preparing to float on the Nasdaq stock market, home to Apple and Google, and hopes to raise around $5bn in its initial public offering in May. That would value the company at as much as $100bn.
