Social networking giant Facebook, which is in the process of going public with a record IPO that could value the company at about $100 billion, has just announced it is buying Instagram for about $1 billion in cash and stock. The popular photo-sharing application had one of the fastest growing user base in the mobile space, garnering around 30 million iOS users in just 18 months, and new users signing up at a rate of more than 2,000 people a minute after its Android client was launched last week.

Facebook Chief Executive Mark Zuckerberg broke the news in a statement posted on his Facebook profile. The young billionaire said that while he plans to integrate some aspects of Instagram into Facebook, Instagram will maintain the experience and continue to operate as an independent company.

That means 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. It's also reassurance that the service won't suffer the same fate as Gowalla.

Facebook has made several acquisitions in the last years and this is the largest yet. Photo sharing or even photo processing applications on mobile devices are nothing new, but factors like simplicity and the community around the service made Instagram a huge hit among smartphone owners.