I remeber a guy from work who is an F1 nut told me that there was case where a team was found out using a flexible rear wing that had a high angle of attack at low speeds but when it hit higher speeds it flexed down and flattened out to cause less drag.
He also reckons that Micheal Schumacer would never have won so many championships if it wasn't for his team "pushing the envelope" of what was allowed in the rules regarding fuel loading, engine power, traction control etc.