User Account Pruner
The User Account Pruner can be used to remove user accounts that have never been activated and (as of upcoming 1.0.1 version) that are not referred to within resource metadata. A delay (number of days) after initial signup can be specified before an account is considered for removal.
Accounts can be pruned once on command, or automatically on a regular basis.
In version 1.0.0 of the plugin, accounts are pruned regardless of whether they are referred to in a resource record. (Usually not an issue unless accounts have been created artificially as part of a collection workflow.)