The problem with huge markets is the same problem you’d have playing squash or raquetball on a court that’s too big. The ball doesn’t have a wall to bounce off of. Huge horizontal markets have no echo chamber, no niches, no easy entry points. To make a system like this work, everyone has to agree on the technology and then there has to be a huge push to get millions of people to make the same decision at about the same time. It might work, but it’s awfully expensive.
In my mind, Seth issue has more to do with relevant messaging and effective marketing than some inherent problem with the size of a market. If you somehow had a monopoly on bringing a product to China (one that could not be duplicated domestically) and it was a product that everyone in China need and had the money to pay for, I’m sure you would sell it.