Update: March 2014 - Getty have announced the end of their flickr partnership
A recent post on flickr makes for interesting reading. It's long been anticipated that flickr would include some way for users to sell their images, and until now there has been lots of debate about how this might be implemented. Because flickr is photo sharing for the general public, it's less likely that photo editors / image users are going to want to wade through screen after screen of pictures of kids and pussy cats. Flickr is also not really the place that photographers think about selling photos; while flickr has many quality images, it is still by it's nature, 'amateur'.