I was under the impression that the People Picker used to be able to query both the underlying authentication types (Active Directory and FBA repository) as well as the User Information List (in /_catalogs/users on each site collection).
However, it looks like this ability to query the users in the User Information List has been disabled in a SharePoint 2010 Cumulative Update, but I can't confirm this.
More importantly, is there a way (like a hidden stsadm command) to re-enable that ability to query the user information list in the People Picker?
I can see some extranet scenarios where it would be very useful (namely allow external users to only pick AD users you have access permissions to a site collection).
Thanks in advance for any feedback!