A key patent that Apple successfully used against Samsung in its multibillion-dollar courtroom brawl earlier this year is at risk following a re-examination by the U.S. Patent and Trademark Office. All 21 claims of U.S. patent No. 7,844,915 -- also known as the "pinch to zoom" patent -- were rejected by the Patent Office today, following a re-examination. Samsung pointed this out in a filing to U.