Flickr is one of the classic stories of a business that didn't recognise its market until it was too late. It was arguably the most popular place for people to post photos and share them online but completely missed the social media bandwagon and found itself usurped by Instagram and Facebook as the preferred way for people to share images. Now Flickr, which was acquired by Yahoo! in 2005, is being sold to SmugMug - a site popular with professional photographers and "visual storytellers".