Horizontal social networks.

The users of horizontal networks form communities who have diverse interests and a wide variety of reasons for using the application. The most popular examples of horizontal networks are:

• Facebook: This application allows groups of friends to publish both public and private messages with text, links, news, photos and videos.

• Twitter: This social network has some unusual features. Users publish short text messages (tweets of 140 characters). The relationships between users are not always bidirectional. One of the most interesting functions is using hashtags to follow interesting events or topics.

• Google+: This social network allows users to create 'circles' of friends in order to share information. They can share photos and form public or private communities.