Ask HN: How ethical are pre-sales? Have you ever pre-sold a product?

Pre-sales are becoming a popular funding strategy for companies, and its effectively 0 interest loans from your prospective users. I am considering to do one.

But Fake Door testing isn't quite ethical. You are selling a product you haven't made yet. Someone might steal your idea before it takes off. You need an audience.

What is your opinion on pre-selling products and the new paid waitlists trend?