Immortal Nobody
Well the Baneling Bust BO I use isn't really an all-in. It's very eco friendly (lol, eco friendly Banelings). But the thing with the FFE, I don't think there's a map in the current pool aside from Shakuras Plateau that has a really narrow opening into the nat. So even if the Protoss does have good FF's, he's still losing that expansion. At the very least.
But then, the whole argument about FF placements is a bit null. So he FF's and you can't get in? Pull back and wait for them to disappear. That's what it means to bait the use of that energy. And it's not like he'll get a force strong enough to stop you in that 15 seconds. That's kinda what I mean. It's up to the toss player to have good forcefields. If he does a forcefield rodeo on your banelings, then you've pretty much lost since he didn't lose anything, or at the very least just some minimal damage. The idea behind this is you have to do damage otherwise you're behind. Unless there is some build I've never seen that makes the perfect amount of banelings that allows you to do damage, but not be behind from it.
I'm not saying it's a bad build or a bad thing to do. Just that it has flaws. And I'm not one of the delusional that somehow think that "All-ins" are bad. Hell, I don't think cheese is bad. Everything has a place in SC2, and if it wasn't supposed to be in the game, it would have been patched out by now.
I could do the same about FFE. The flaws it has are the fact that it is easily killed off by all-ins if you cannot prepare for them correctly. And it usually isn't easy to just blanket prepare for anything, since zerg has many options. You choose the wrong one, and you are behind in eco, or just flat out die to another one you didn't prepare for.
I just like to point out flaws in builds so you can adapt and/or prepare for them.