GCHQ's Karma Police: Tracking And Profiling Every Web User, Every Website
This means that it is certain that many -- perhaps millions -- of UK citizens have been profiled by GCHQ using these newly-revealed programs, without any kind of warrant or authorization being given or even sought. The information stored in the Black Hole respository, and analyzed with tools like Samuel Pepys, provides unprecedented insights into the minutiae of their daily lives -- which websites they visit, which search terms they enter, who they contact by email or message on social networks. Within that material, there is likely to be a host of intimate facts that could prove highly damaging to the individual's career or relationships if revealed -- perfect blackmail material, in other words. Thanks to other Snowden documents, we know that the NSA had plans to use this kind of information in precisely this way. It would be naive to think it would never be used domestically, too.
You can find the report here.