JamiiForums is a large Tanzanian discussion and whistle blowing platform, which is notable for its users criticising the government and exposing corruption. As such, it's in direct conflict with the government and therefore at risk of disappearing.
In 2016, the founders of JamiiForums were arrested and charged with obstruction of justice. In June 2018, JamiiForums shut down for a few days shortly before a new regulation regarding online platforms came into force in Tanzania because the relevant authority TCRA had not granted their registration as a service provider (rather than a content provider).
As of August 2018, there are 27.6 million posts by 451k users in almost 1.2 million threads.