I understood PG's point differently. My understanding is that he is suggesting an angle of attack in which carefully crafted manual reviews (that do dot scale)

I understood PG's point differently. My understanding is that he is suggesting an angle of attack in which carefully crafted manual reviews (that do dot scale) can be used to bootstrap a product that does scale thanks to something else (e.g. collaborative filtering). All of this being on a niche domain where you can drive a wedge into the mediocre performance of Google (online shopping probably being the worse possible choice, but there are many others).