The only reason that picture could possibly be considered "controversial" is because she looks so good in that position. If SI had put a skiier that looks like Rosie O'Donnell in the picture instead, nobody would have even noticed.
There is nothing wrong with this picture.
People need to learn that even though we do have a number of "rights" as citizens, no one has the right to never be offended. If rabid feminists are offended by this cover, then don't buy the magazine.