In the new world of on-demand everything, you’re either pampered, isolated royalty — or you’re a 21st century servant.Angel the concierge stands behind a lobby desk at a luxe apartment building in downtown San Francisco, and describes the residents of this imperial, 37-story tower. “Ubers, Squares, a few Twitters,” she says. “A lot of work-from-homers.” And by late afternoon on a Tuesday, they’re striding into the lobby at a just-get-me-home-goddammit clip, some with laptop bags slung over their shoulders, others carrying swank leather satchels. At the same time a second, temporary population streams into the building: the app-based meal delivery people hoisting...