I found it an interesting case study b/c these guys were not waiting for network confirmation (sacrificing security for speed) and also the receipt of the bictoins automatically gave you the full picture without the user needing to do anything.
oh, as long as it is for a "case study" / research: http://bittit.info
and actually, the interesting thing is that by far the majority of images are not erotic or nsfw. the site simply provides a great way for a photographer or image creator to sell their work. for sale are things like bitcoin wallpaper images, funny cat photos, nature photos, drawings and more.
the reason they might accept on 0/unconfirmed is that even if you successfully double spend on them, by giving you access there is no theft occurring. you didn't deprive the artist of something the artist had previously.