Web 2.0 refers to interactive websites and services. The massively multiplayer online role-playing game World of Warcraft has over 11.5 million subscribers, generating more revenue than some countries' GDPs. Blogging allows people to share thoughts, information, and debate views while documenting life experiences. Gamification takes non-fun activities and adds interactive or competitive elements. Internet memes involve adding funny captions to pictures, while trolling refers to pranking or posting inflammatory comments online.