By itself, none; a problem is caused only if the coder is forgetful and/or disorganized.
Implicit control flow simply removes the needs for *goto after *elseif, *else and *choice. So besides not needing to use *gotos in *elseif and *else (as you’ve said, it’s good because it cuts down a lot of unecessary labels right under those *elseifs and *elses) it transforms the *choice into a *fake_choice.
As in, if it does not encounter a *goto it will simply continue down the file. So if the coder makes a mistake and forgets to put something there the code will continue down the file down and that’s it. Nothing else is changed, you can still use *gotos wherever you want, including on *choice.
The great gain of implicit control flow on is to cut down on *gotos and *labels after the *elseifs and *elses, especially if you use that a lot. It also avoids workarounds of very long sections of *if, *if, *if… etc instead of a more organized *if, *elseif, *elseif, *elseif…, *else section (as is more usual in programming).
These claims are blown out of proportion; this is not absolute. I don’t want to start bickering but it’s getting tiresome having to reply to another total misinterpretation of yours once again in the same week.
If one author made a mistake about having half their game skipped the mistake is on them, not implicit control flow. By usint this they had in mind that it would cause something to proceed down if a *goto was not included. The fact that the code did exactly what it was supposed to do was not an error; the mistake was the author forgetting to include something.
I provide this alternative (and will continue to do so) because it’s helpful and because it’s optional. If you don’t like it or are not capable of using it, don’t use it. Choice of Magics is a game produced and published using implicit control flow, if you don’t believe me, just go look at its code in its demo and you will see it there after all variables are created. Don’t claim your opinions that it’s only for testing or it shouldn’t be used as fact; it is in use by an official CoG product. If you want, go ahead and tell the author of Choice of Magics they made a mistake in using it.
Choice of Magics code snippet
For others reading this, instead of going by arguments such as “don’t listen to X, it’s bad” with poor reasoning behind it, read my explanations and link above to the official CoG staff announcement about it and make your minds whether it’s something YOU want to use it or not.
Besides, next week I’m gonna make a wiki page about implicit control flow and *gosub params because I think they are valuable tools for coders and authors. They’ve been announced a while ago and not well known; I want to correct that and make them known for others that are interested on their uses.