How to think about this :
2) Facebook (as all the big social network are) is in the "find where people are" business. ("locative services")
You don't even have to go conspiracy theorist (Facebook part owned by the CIA) to see that Instagram gives Facebook another massive injection of photo data about who is where with who and when. And that this can be mined for all sorts of valuable information and patterns.
FB can discover relationships between people and places that no-one has explicitly told them about. They can tell advertisers where you like to hang-out socially. And who with. You think they aren't trying "sentiment analysis" to try to figure out whether people in photos are happy or sad? What's it worth to FB to know which bars in London have the happiest customers? Or which companies have the most drunken
employees? Or that you like motorcycles?
Google are after this data too. That's why they just brought out wearable "glasses" that can tell Google what you're looking at. Instagram might very well be Facebook's response in the "grab" for rich visual data streams.
Some people are noting the potential threat to FB from Pinterest too and saying this is a defensive move. Today is a great day for Pinterest. Someone will be trying to snap that up soon.