I'm in the San Gabriels 2-3 times a week, often cooking something for lunch on dayhikes. In talking to the rangers, while their biggest concern is wood fires, they are dead serious about alcohol stoves as well. It has to be pressurized gas or Sterno type fuel (ironic being that Sterno is actually jellied alcohol, not jellied petroleum as written in the regulations). I specifically asked about Esbit more than once, explaining the reasoning Hikin Jim gave (sound reasoning IMO). Each time they said no, its not allowed under the current regulations. I talked to the Mt. Baldy Fire Chief as well, he said that his biggest concern is also wood fires, but that the Forestry department sets the regulations, not him.
I'm likely to get flamed by alcohol stovies for this, but here goes. Are alcohol stoves inherently a greater fire danger than a canister stove? I would say so, depending on the type. Penny stoves and the like are in that they are more difficult to extinguish quickly if needed. You can invert a metal cup over them, but you have to be ready with one. Cat cans and tea lights will spill their load if knocked over. A Zelph Starlyte can be covered and extinguished quickly and very little (if any) fuel comes out if knocked over. I own and have used all of the aforementioned types, and a few others. Regardless of the type, alcohol flames can be very difficult to see during the day and an inadvertent spill can go unnoticed. In the end, its the person using it thats most likely to be the cause of a fire getting out of control, but there would appear to be far more room for "accidents" with an alky stove.
I agree with Hikin Jim (except Esbit where prohibited). I'm a fan of wood stoves, as well as alcohol and Esbit (and campfires). But for right now, I agree with the regulations, because its a tinderbox in the mountains right now (my co-workers are trying to contain a brush fire in the foothills as I'm typing) and because I love my hiking trails. Icehouse Canyon is my favorite trail in Southern California, I'd hate to see it blackened (again) by carelessness, and out of the hundreds who hike there every week, I see more than a few of them acting somewhat less than responsibly.