You know this acquisition is different because Mark Zuckerberg wrote a post about it:
For years, we've focused on building the best experience for sharing photos with your friends and family. Now, we'll be able to work even more closely with the Instagram team to also offer the best experiences for sharing beautiful mobile photos with people based on your interests.
We believe these are different experiences that complement each other. But in order to do this well, we need to be mindful about keeping and building on Instagram's strengths and features rather than just trying to integrate everything into Facebook.
That's why we're committed to building and growing Instagram independently. Millions of people around the world love the Instagram app and the brand associated with it, and our goal is to help spread this app and brand to even more people.
We think the fact that Instagram is connected to other services beyond Facebook is an important part of the experience. 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.