It's inevitable with the efficiencies brought by technology. You need fewer and fewer middlemen, and so you end up going vertical.

If anything this makes things more inefficient, because I bet a lot of core infrastructure will have to be laid out many times over.

It doesn't seem to be enough to offset the gains from the efficiency of scaling horizontally. Each product or service, when provided or assisted by computers, requires fewer and fewer humans which are the most difficult to scale up, so an organization can set that up and then move up and down their supply chain. It might be a temporary benefit though, because once it's big player vs big player they won't be able to easily extract value (or one of them will kill the other and get even bigger, which is bad for the rest).