I used to work for a pretty big social media company. They all use anycast, not reverse proxies, with a multi-region setups. You don't need to have strong consistency on the data side of things, so you're incorrect. The typical setup is a pop ring equipped with a common anycast IP, with private interconnects to other locations. Updates are made to a local (or preferred) colo, then synced to the others. Because people tend to not move around to much you can rely on location to choose a preferred colo, and because this is not a live application, you don't need strong consistency between the colos. Each user seeing a slightly different thing doesn't matter since content is intrinsically ordered.