[ville]

Why would I want to build that product in exchange for equity, which will probably be worthless?

If you don't want to spend money on your idea, chances are it is even more likely to fail than an average startup. This feels like a way to exploit talented and gullible people who want to work at startups.

EDIT: typo

[hoursforequity]

Why would you ever agree to work for a company that builds useless products, regardless of pay?

In our experience, founders have spent money on their ideas. However, many bootstrapped startups (particularly the hardware engineering companies we have helped) don't have enough for talent and prototyping. When equity is issued these companies are bringing on partners, not gullible engineers. Just my two cents, please let me know if you see it differently.