Each change has a single user who is responsible for it. Most builds have a set of changes: the build generally represents the first time these changes have been built and tested by the Buildbot. The build has a “blamelist” that is the union of the users responsible for all the build's changes.
The build provides a list of users who are interested in the build – the “interested users”. Usually this is equal to the blamelist, but may also be expanded, e.g., to include the current build sheriff or a module's maintainer.
If desired, the buildbot can notify the interested users until the problem is resolved.