Probably the vertical approach started from a need to have better search and be able to describe a certain type of object/activity. Think about it for a minute: to be able to search you have to be able to describe what you want. To be able to match a description you need to have a structure in place (e.g. the attributes of a car is a structure).

Sites like Craigslist offer a GENERIC way to DESCRIBE MANY objects/activities therefore they offer a GENERIC way to SEARCH for many objects/activities. Sites like AirBnB offer a SPECIALIZED way to DESCRIBE ONE TYPE of object/activity and they have a SPECIALIZED way to SEARCH for that one object/activity.

What if we have a SPECIALIZED way to DESCRIBE MANY activities/objects and a SPECIALIZED way to SEARCH for MANY activities/objects?

That's what I'm trying to do at https://pinad.com.au. Currently I have 81 structured categories and hundreds of attributes and options. All of them allow a specialized description and a specialized search. Would this be a better alternative for a centralized marketplace?