It probably depends on the person and how much they sweat; I'd imagine I sweat more than the average person and I'd be nervous about staining this.

Don't get too nervous - it will just make you sweat more

And, more important, how much they type. I'd say that for a machine aimed at teenagers this might not be a good idea. Time will tell.

As a teenager I had a sweaty spotty face and armpits and stank, had a chronic hairdo, poor social skills etc. but I do not remember my hands being sweaty.

Were yours?

Thankfully I am past all that now, apart form the chronic hairdo, the spotty face, poor personal hygiene, awful social skills....... etc. etc....

They don't have to be constantly sweaty. repeated friction and skin oil from palm of hands is enough to discolor palm rests in normal laptops. This is an even easier surface to discolor / stain.

It will depend on how much you type, of course, and it will be different for different people but I wish they'd have chosen another material even though this one looks gorgeous.

Sweat is enormously varied in composition. Some guitarists can corrode a brand new set of strings in a matter of hours, while others can play for weeks on the same set. Some people have sweat that's acidic enough to turn a silver flute black or strip the lacquer from a violin.