I didn't look up the technical definition of "business model" but it's pretty clear to me that their goal is to dominate vertical search and be a trusted source

I didn't look up the technical definition of "business model" but it's pretty clear to me that their goal is to dominate vertical search and be a trusted source of information. They are following the same path Google did. When Google started the didn't know how exactly they'd make their money. Their goal was to be the best (and least intrusive) search and monetize later. Being the primary, trusted source of information in a bunch of vertical search areas has obvious value. One potential avenue is to become a sort of university. They know the areas that people are asking lots of questions about and could setup a course to cover the topic. They don't actually have to be the ones to setup the course. They have the information to sell to someone who would setup the course. The preceding is just an example of how being the leader, that is having the information, is the business model (or goal if you will). Trusted information has value.