Online Social Networks (OSNs) have become one of the most popular application of the daily life of users in the worldwide. Today the number of Social Media users is about 3 billion, and this trend increases year per year with high impact on the privacy issue. During the last years, decentralization of social services has been considered a big opportunity to overcome the main issues in OSNs. Blockchain technology represents today the most well known decentralized technique, which has been taken into account to develop the new generation of decentralized social platforms. Nevertheless, the real benefit of the introduction of blockchain technology in real social platforms is still unknown. In this paper we propose an overview of the main Blockchain-based Online Social Media platforms. We describe in detail these platforms by highlighting the main features and services they offer, but also the common drawbacks of these platforms. Finally, we propose a new model of Blockchain-based Online Social Network, which takes into account the role of the user as the center of the system, instead of the role of the content as in current proposals.

在线社交网络（OSN）已成为全球用户日常生活中最受欢迎的应用程序之一。如今，社交媒体用户的数量约为30亿，并且这一趋势每年都在增加，对隐私问题产生了重大影响。在过去的几年中，社会服务的权力下放被认为是克服OSN中主要问题的重要机会。区块链技术代表了当今最著名的去中心化技术，在开发新一代去中心化社交平台时已经考虑到这一点。然而，在真正的社交平台中引入区块链技术的真正好处仍然未知。在本文中，我们提出了一个主要的基于区块链的在线社交媒体平台的概述。我们通过重点介绍这些平台提供的主要功能和服务，以及这些平台的常见弊端来详细描述这些平台。最后，我们提出了一种基于区块链的在线社交网络的新模型，该模型考虑了用户作为系统中心的角色，而不是像当前提案中的内容角色。