I wish F9 would raid the OAK-SoCal market, multiple flights per day in each market. As long as I have Gold status I would book them up to about $80, if only to make a personal statement about Southwest's so far unsuccessful attempts to gouge me.
Oakland is an interesting one, and I could certainly see an argument for Frontier returning there. There's a very large population in the East Bay, and it's a long way to SFO. Do people avoid it due to its environs? A couple of years ago I needed to stay in the area and read some airport hotel reviews which were, to say the least, concerning. At least one of those hotels later closed due to crime.