The study deals with the role of reciprocity in evaluation of amateur photography on the web application Flickr. The primary goals of Flickr are to share and organize images on-line. Although appreciation of the photos is not among them, it comes as a logical consequence of sharing images and presents the basic activity of the participants. This appreciation tends to be reciprocal and becomes a social norm of Flickr community reflected on the level of the organized groups as well as on the more personal level of the participants' contacts and friendships. The informal networks of the contacts and friends significantly influence success of the images measured quantitatively by several characteristics (views, comments and favourites) and also indirectly mediate success on the level of formal networks presented by the organized groups. While on the level of the contacts and friends reciprocity presents rather implicit social norm, on the level of groups it is often requested by the rules and therefore presents declared social norm supported by the sanctions. In both cases, the non-reciprocal participants do not have a chance to achieve any significant success in the terms of the Flickr community.