User blog comment:Daniel Baran/Search Developments: Big Picture/@comment-4528041-20120508195723/@comment-26686429-20120509063055

The terms of use state (emphasis added):

Not to intentionally block, remove, or otherwise obstruct the proper functioning and view of advertisements, and/or user interface and functionality by other users, including but not limited to changing or adding javascript or CSS changes to the Service that would prevent the proper display or function of advertisements and/or user interface and functionality;