We were bumping into limits on the config format in the Blacklist
plugin. So, added new tables for nickname and homepage blacklists, and
changed the plugin to use those instead of config file (actually,
still uses config file in addition, for compatibility).
First version of blacklist plugin. Replaces custom code in identi.ca's
config.php, which was getting scary and long. Also correctly handles
changed nicknames or URLs in profile settings and using 'forbidden'
URLs in notice text.
