Aamerena,
Still illegal. To share costs, the travelers must have a common purpose. If you and a friend were to, for example, fly to California to visit Disneyland (or just so each of you could build hours), you could split the cost of the flight. Advertising for someone who wants to go to California on Craigs List (or anywhere else) would be seen as holding out an offer of air transportation. There is no common purpose for the trip--you are doing it to build hours and the passenger is doing it to get to California.