Twitter blew up Monday with news of Facebook’s acquisition of photo filtering and sharing mobile app Instagram. Part of the buzz was grumbling from Instagram fans, worried that Facebook would disassemble a beloved app and use its parts for scrap; another was bemusement at the price tag on the deal – a cool billion dollars (which works out to about 76 million per employee); the third – and to our minds the most interesting – topic of discussion centered around speculation as to what, exactly, Facebook does plan to do with Instagram, and how the industry leader in social will again evolve…and take the rest of us along with them.

Facebook’s biggest medium is photos – over 200 million are uploaded to Facebook every day. The biggest bonus Facebook gets for its billion is providing a value added service to its users to share more individual photos, increasing the appeal of Facebook timeline and make it easier for people to share photos. Bottom line: sharing cool stuff we’ve seen or created is ideally what it’s all about.

Even if a few of Instragram’s 30 million users do unsubscribe in a hasty huff, the acquisition is still a pretty significant bump for Facebook, which is clocking in at 800 million subscribers, but facing diminishing returns, having fairly well saturated the US social media market.

For all the buzz, it’s interesting to note that email, not social media, is sill the number one most-used tool for sharing content. More content is still shared via email than by any social media platform, Facebook included. (Exception: high schoolers, for whom Facebook just edges out email as the sharing tool of choice). An email is still tops in terms of timeliness, as well – 91% of people check at least once a day, which is more than any social media application sees.