On June 11, 2012, the FY 2013 H-1B cap was reached. USCIS announced on its website that it has received enough H-1B petitions to exhaust both the advanced degree and regular caps.
Per the USCIS website, the agency will reject cap-subject H-1B petitions requesting an employment start date in FY 2013 that are received after June 11, 2012. FY 2013 covers the period from October 1, 2012, through September 30, 2013.
USCIS states that it will continue accepting H-1B petitions that are exempt from the cap, as well as DOD cooperative research worker H-1B petitions and Chile/Singapore H-1B1 petitions, which include a start date in FY 2013.
Last fiscal year, the cap was reached at the end of November, so this is much earlier, but not unexpected.