In the fallacy of an appeal to indirect consequences, also known as a slippery slope or domino theory, remotely possible but usually very negative effects are presented as the automatic consequences of a course of action or belief, with the idea that the sheer negativity of those possible effects will be sufficiently persuasive to ensure the rejection of that course of action or belief. In other words, if I can make it seem that your decision, however justified in itself, will produce certain and unavoidably negative outcomes, you will probably change that decision. The issue in a fallacious appeal to indirect consequences, therefore, is how certain and unavoidably negative these effects are. Let's consider some examples of arguments about smoking.
Kay's consequences are more dire--illness and death--and more remote. These consequences don't always happen to smokers, and even if they do happen to Maya, the onset may be years off (depending, perhaps, on how much Maya smokes and for how long). Yet there is an impressive body of scientific evidence that almost everyone is aware of, which establishes a causal link between smoking and serious illness. At the very least, then, when dealing with Kay's argument, Maya would have to confront the strong probability that smoking is at least increasing her chances of contracting a serious illness significantly, and make her decision accordingly.
No one wants to end up "broke, unhappy and alone," but Ray's argument is obviously the most tenuous of the three. Notice the steps necessary to accept Ray's argument: that the connections are automatic, first between an addiction and a personality disorder, then between having that disorder and succumbing to pressure, then between succumbing to pressure and losing one's job and personal relationships, and finally between losing those relationships and ending up broke, unhappy, and alone. Those many questionable steps are what gives this fallacy its popular names, "slippery slope" and "domino theory," because once you begin accepting its tenuous connections, it's downhill or unstoppable from then on. Ray's argument, then, is a good example of a fallacious appeal to indirect consequences.
Of course, not everything with a long series of consequences is a fallacy; you must learn to differentiate between a chain argument and a fallacious appeal to indirect consequences. Both can have the form "If P then Q, then R, then S, then T . . ." but a chain argument is built on plausible causation and is confirmed a step at a time. In a slippery slope fallacy, the plausibility of its causal links is ignored, and the focus is entirely on the dire results at the end.
Wishful Thinking is, in some ways, a fallacy opposite to an appeal to indirect consequences. In wishful thinking, an extremely positive outcome, but one just as remote, is suggested in the hopes that it will distract from the merits of the case at hand. It's a slippery slope to support a new sports stadium in a city with the argument that, otherwise, no professional teams will play there, and without professional sports, businesses will begin to leave, jobs will be lost, taxes will go up, and property taxes will go down. On the other hand, it's wishful thinking to reject that sports stadium with the argument that the money could be better spent improving public transportation and education, which will attract more businesses so that unemployment and taxes will both go down. Neither "stadium equals disaster" nor "no stadium equals paradise" is very realistic, because both assume that remote possibilities are certain and automatic.