If the stuff is efficient enough as a source for gasoline replacement generation to be worth making gasoline from, subsidies shouldn't be necessary to ensure a sufficient stock. If it requires subsidies, that indicates a big problem with that plan. Unless the main goal is to reduce foreign oil independence. But I'm skeptical that that goal is remotely feasible with biofuels without making serious compromises in food-generating land. We should be spending this effort and funding on improving battery tech and creating business models that make electric vehicles appealing (swappable leased batteries, for example), as well as improving nuclear power tech to feed those vehicles.

EDIT: Algae seems like it could be promising, assuming we could find a way to mass farm it without disturbing ocean food cycles.