You will hear people say that due to pollination, air pollution, or the intervention of the Alien Overlords (OK. I made that last one up. But people get a little extremist at times) there is no such thing as organic food any more.
Yes, any government official can be impeached - Presidents, Legislators & Judges, etc. But you can't impeach people for doing a bad job. Impeachment is necessarily dependent upon a charge of criminal or significant unethical behavior to warrant removal. Yes, Granholm is awful, but we're stuck with her for 4 more years.
Two presidents have been impeached; the Democrats Bill Clinton, in 1998, and Andrew Johnson, in 1868. Neither was found guilty by the Senate in their subsequent trials. Republican Richard Nixon was threatened with impeachment following the Watergate scandal in 1974, but resigned before the vote on his impeachment could take place.