[_delirium]

Residential hotels with small rooms used to be sort-of an approach to this, though they weren't all the way to capsule-like. Some of them were fairly nice and had developed communities as well (usually of writers or artists).

Due to a mixture of social shifts and demolitions/conversions, though, the remaining ones are generally extremely run down and verging on squalid, so it's not as much an option anymore. SF still has some SROs in the Tenderloin, but they are not particularly well-maintained or clean; the upper end of the residential-hotel category has been demolished or converted into condos or regular hotels.