There are two things wrong with this analogy.
One is that this isn't a real value change. You gained the ability to appreciate sex as a source of pleasures, both lower and higher. As a child you already valued physical pleasure and social connections. Likewise, just as the invention of pianos allowed us to develop appreciations for things our ancestors never could, future technology will allow our descendants, we imagine, to find new sources of pleasure, higher and lower. And few people think this is bad in itself.
The more fundamental problem with the analogy - or rather, the question that followed it - is that it asks the question from the perspective of the adult rather than the child. Of course if our descendants have radically different values, then unless their ability to alter their environment has been drastically reduced, the world they create will be much better, from their perspective, than ours is. But the perspective we care about is our own - in the future generations case, we're the child.
Consider a young law student at a prestigious school who, like many young law students, is passionate about social justice and public service. She looks at the legal profession and notices that a great deal of lawyers, especially elite lawyers, don't seem to care about this to the extent that her age-mates do - after all, there are just as many of them fighting for the bad guys as the good guys, and so on and so on. Suppose for the sake of argument that she's right to conclude that as they get socialized into the legal profession, and start earning very high incomes, and begin to hobknob with the rich and powerful, their values start changing such that they care about protecting privilege rather than challenging it, and earning gobs of money rather than fighting what she would see as the good fight. And suppose further that she sees, accurately, that these corrupted lawyers are quite happy - they genuinely do enjoy what their work, and have changed their politics so that they genuinely do get even moral satisfaction from it. And suppose she sees that she's not, in any measurable respect, different from all those other young idealistic law students that turn into old wicked lawyers - aside, perhaps, from coming to evaluate just these facts.
Is it rational, given her values and assuming her conclusions above are true, for her to take (costly, but not catastrophically costly) steps to not become corrupted in this way? After all, if she is corrupted, her future self won't consider herself worse off - in fact, she'll look back at her youthful naivete thank her lucky stars that she shed all that!
By even considering how lawyers observably change, it would seem that our idealistic young law student is already infected with the memplex of perspective. Nevertheless, nigh tautologically, the future offers new perspectives as yet unappreciated. After all, as for any question of memetic self preservation of integrity, you have it simply given as premise, that the greedy future lawyers are entirely honest with themselves. Actually, memes only exist in context of their medium, being culture, an ongoing conscious and social phenomena that governs even Axiology.
Ben Goertzel:
Robin Hanson:
We all know the problem with deathism: a strong belief that death is almost impossible to avoid, clashing with undesirability of the outcome, leads people to rationalize either the illusory nature of death (afterlife memes), or desirability of death (deathism proper). But of course the claims are separate, and shouldn't influence each other.
Change in values of the future agents, however sudden of gradual, means that the Future (the whole freackin' Future!) won't be optimized according to our values, won't be anywhere as good as it could've been otherwise. It's easier to see a sudden change as morally relevant, and easier to rationalize gradual development as morally "business as usual", but if we look at the end result, the risks of value drift are the same. And it is difficult to make it so that the future is optimized: to stop uncontrolled "evolution" of value (value drift) or recover more of astronomical waste.
Regardless of difficulty of the challenge, it's NOT OK to lose the Future. The loss might prove impossible to avert, but still it's not OK, the value judgment cares not for feasibility of its desire. Let's not succumb to the deathist pattern and lose the battle before it's done. Have the courage and rationality to admit that the loss is real, even if it's too great for mere human emotions to express.