There's a term for when everyone buys something just because you can sell it to someone else for more later.

It's called a bubble.

Yep but when our 401ks auto buy in there's a bit of a stop gap. Also I think the bigger reason is that with tech people expect a nonlinear impact. Amazon being the example. So not only revenue break even but market growth and new market opportunities.

It's only a bubble if it busts. And stock does have value, and if the business it represents have growth, the equivalent value must also grow.

And in any case, if someone else feels that the stock is worth more, and thus pay more for it, what's the problem?

The term of art is actually “greater fool theory”

Sounds exactly like Bitcoin!