Recently I developed a tooltip functionality in SharePoint 2010 which queries the pages list, fetch the title & description and renders it as a <div> element.
Problem Description:
It was working fine when the user is logged in, but when I access the site as anonymous user, it gave me error “the method GetItems on List with ID {guid} is blocked by administrator”.
So, after a quick googling I found the solution, that there are some restrictions in client object model for anonymous users. These restrictions are called client callable settings in SharePoint.
Nikhil Doomra 