Great tongue-in-cheek article by New York Magazine's Paul Ford on why Instagram sold its soul to Facebook. And while I do get that some people are upset about it, I don't think anyone who would say no to $1 billion dollars.
Now consider Instagram. If Facebook is a sprawling, intertextual garden of forking pokes, Instagram is no more complex than a chapbook of poetry: It lets you share pictures with your friends and keep track of strangers who post interesting pictures. It barely has a website; all the action happens on mobile devices. Thirty million people use it to pass time in the bathroom. You can add some fairly silly filters to the photos to make the pictures look like they were taken in the seventies, but that's more of a novelty than a requirement. So that's Instagram. It's not a site, or an app. What it is, really, is a product.