Abstract
Flooded by the propagation of false or biased news in the Web, people tend to resort to social networks to read posts from reliable sources, exchange commentaries with trustworthy parties, access first-hand content, or cross-check information that appears in news outlets. However, platform providers like Facebook or Twitter can ultimately decide about the contents exposed to each user. Anecdotal evidence suggests that such platform providers are prone to pressure by political or economical agents, and may be ideologically driven to hide messages or block certain users, thereby impairing users’ ability to freely access rightful information.