It is utterly implausible that a small coffee's worth of caffeine, when mixed with what is roughly five shots of liquor and two cans of soda, has any substantial effect. The same cannot be said for other stimulants (taurine, guarana, etc.), which we know much less about and have some reasons to be suspicious about.
The maker of Four Loko moved ahead of the ban, saying they would reformulate their product to leave out all the stimulants, not just the harmless one. Assuming they make good on that promise the resulting product will be the equivalent of store-brand soda with cheap vodka, which I suspect is cheaper and easier to acquire in most jurisdictions, and can be mixed to taste. Perhaps Four Loko has enough brand equity to keep selling in spite of this. If that is really the case, perhaps the authorities should be investigating marketing practices rather than ingredients.
But it is inevitable that someone -- one of the other four market incumbents or someone else -- will fill the void with a product that dutifully leaves out the caffeine but ups the other stimulants (which are harder to find in, say, the cooler of soda that is sitting right next to the cooler of booze at a party). This might turn out to be relatively low-risk, like we know the caffeine is, but we do not know that. It seems plausible that the much talked-about case of a heart attack that was attributed to one of the existing drinks was caused by the taurine, which relatively few people are used to consuming and which stimulates the heart in particular; it was almost certainly not caused by the one cup of coffee worth of caffeine.
So, we shall see if FDA succeeded in killing anyone by banning something that is very low risk while doing nothing important to discourage the high-risk alternative. (See also: electronic cigarettes.)
It is really quite remarkable that news reporters have let FDA pretend that they can keep people from mixing alcohol and caffeine by banning four products that put them in the same can. If anyone needs a recipe for making caffeinated alcohol using common household products, I would be glad to provide it for them.
But that was not really what this was about for FDA -- it was pure muscle flexing, trying to see what they can get away with and pushing the boundaries of how much they can meddle in people's personal choices.
This is quite a bad sign. My personal bias is that the world is probably made a better place through the removal of these products (for an extra few dollars the kids can drink good beer and Starbucks). But, first they came for the Four Loko and I did not object because I did not like Four Loko..., and so on.
The press release suggests that this was the proudly implemented pet project of FDA's Nanny in Chief (I don't remember his exact title, but I think it is something like that), Josh Sharfstein, who may be the greatest threat to the well being of Americans that almost no one has ever heard of. It seems unlikely that any of the targeted manufacturers will have the resources to fight this (notice that FDA arbitrarily avoided sending notice to the much more influential makers of such caffeinated alcoholic beverages as Kahlua and Starbuck Liqueur -- an interesting point that would almost certainly be grounds for challenging the action if anyone involved had the resources to stand up to the FDA). The feeling of unmitigated power that this will create will inevitably lead to further nanny attacks.
No doubt also that the unchallenged perversions of the science will encourage more such behavior. Those who were gunning for these beverages made repeated pseudo-scientific claims (let's be frank: lies) about the supposedly known effects of mixing caffeine and alcohol which defied common sense and were not supported by evidence. But they got away with it, so they know that they can do it again.
So when does the caffeine in Coke get declared an "unsafe food additive"? If the new trend becomes mixing Mountain Dew and vodka into homemade Four Loko (minus the possibly actually bad ingredients), will Sharfstein and company ban Mountain Dew? Probably not because its manufacturer has enough lawyers and lobbyists to fight back and perhaps even consumers would stand up for themselves. So instead, they will keep chipping away around the edges, attacking targets that are too weak to stand up for their legal rights or for good science, banning things just because they can, regardless of whether the ban will help or is even rather likely to cause harm, as in the caffeine targeting (or, of course, attacks on low-risk alternatives to smoking). If things go their way, they will eliminate low-risk nicotine products, Mountain Dew, and Coke, and eventually come for our Peet's Coffee, but by then there will be no one left to stand up to them, because we will all be too groggy to fight back.