I would like to see a plugin that places new users in a moderated mode until an admin decides that they are not a spambot/flamer/etc. Moderators should be notified every time a moderated user posts or creates a conversation. The post/conversation will be in a pending/invisible state until a moderator approves it. The moderator can then take the user out of moderated mode. Users could also be placed back in moderated mode, if the user is questionable..