You have cases of each of these, right?
Perfectly healthy but depressed people acting on momentary impulse: This has been going on for
years in the Netherlands, so this was hardly even a predition.
Death-fascinated doctors... like Kevorkian, gain a legalized-murder playground: I cited an example, only he did it illegally (actually, Kevorkian was a two-fer, some of the people he killed were depressed rather than terminally ill).
Greedy relatives with POA "assisting" Granny and Gramps if they are too "obstinate": Do you seriously doubt healthcare POAs have already been abused to withhold medical care for treatable (= potentially stoppable/reversible)? It's a very tiny step from killing by withholding care to killing by DAS.
If ZPG or VHE folks gain government power, an obligation to die by a certain age: This was the one,
possibly, "out there" prediction I made. That acknowledged, the
Zero Population Growth people have been around since 1968, and the
Voluntary Human Extinction Movement has been around since 1991. These are far from new ideas. Further, the medical community has had for well over a century doctors who favor killing the "unfit" and aged. Hitler actually did it, in accord with his view of "unfit", but it was an idea that had been around EuroLand for decades before.
I think it beyond doubt that there are Peter Singer equivalents out there who are preaching their modernized version of this 19th century idea. To be sure, the US is, right now, far from buying into the idea of an obligation to die; 35 years ago the idea of same-sex marriage was unthinkable outside of very small activists' circles. I think creating a tool the ZPG/VHE people could use to implement their goal of reducing the Earth's human population is horribly unwise.
Edit: Geez, BD, give me a few minutes to find f2003b's post and type a response. Further, I don't type 180WPM, so you posted your 06:49:55 PDT post while I was typing my 07:07:35 PDT post, and you posted your 07:30:53 PDT post while I was typing this response to f2003b.