Facebook’s $1billion purchase of Instagram solidified one of the hottest social trends: Photo images have huge engagement value over text. Another photo site, Pinterest, has recently been commanding the airwaves, claiming 10 million users and “the fastest growing standalone site ever”.

Photosharing is not new. Flickr and Photobucket paved the way for people to share photos online. It was so much easier to upload pics from a family picnic and send members the link immediately following the event. But apart from commenting, there was never really a sense of community.

What Pinterest and Instagram have done is create a “sharing ecosystem” that goes beyond sharing. They encourage expression, curation and validation. As the graphic below shows, sharing becomes a complete process with built-in marketing that produces feedback.  As a result, these two sites provide a content marketing venue that drives added visibility for people who have other properties like websites or blogs.

Pinterest has been addictive for me since the get-go. I immediately got hooked on the different images I saw on the site. As a user, you can create your own “boards” ie curate your own category of images; you can also “repin” (similar to “like”) other people’s images so they show up on your profile. By doing this, you begin to favour certain user’s boards, follow them and begin to build your own community.

My “Pinterests” include fashion I typically buy, nude art, infographics, funny stuff, favourite places and books I like. I also “pin” personal pics that I’ve taken from my iPhone and develop new categories as I go along. Sometimes I spend a good 10 minutes just looking and repinning from other boards. It’s this genuine act of sharing and making suggestions to add to others’ collections that makes Pinterest a true community.

Instagram is just as addictive, but it has Pinterest beat because it’s all-mobile – which is likely to benefit Facebook’s own mobile application. Also unlike Pinterest, most of the images on Instagram are original photos. Instagram adds a layer of location-based sharing plus allows you to edit your images before you post. Your home feed is a dynamic collection of your network’s photos, that include a collection of likes and comments.

Now that Instagram is part of Facebook, your new photos will automatically feed into Facebook’s Open Graph and display as a recent activity. This means that Facebook will be reaching out beyond its current domain. As Mark Zuckerberg said: “We think the fact that Instagram is connected to other services beyond Facebook is an important part of the experience… We will try to learn from Instagram’s experience to build similar features into our other products.” This may help to explain why he was willing to spend so much money.