Well, per Steve Yegge's original post, it's distribution in general. My understanding of his general argument is that when distribution is controlled by Amazon, everybody buys everything from Amazon. When distribution is controlled by thousands of independent drivers, everybody buys everything from thousands of independent businesses (like the couple selling food out of their kitchen that he mentioned) and the cost of starting a small businesses goes way down. For a related argument that vertical integration, especially with respect to distribution, leads to homogeneity, see www.theatlantic.com/business/archive/2018/01/craft-beer-industry/550850/

I've read that the biggest problem in B2C businesses in general is often distribution, so I think the idea is that if grab is successful, they'll boost southeast Asian entrepreneurship and collect a portion of all of that growth