Ask HN: Liability insurance for a startup

A friend is nearing the completion of their site and they are now trying to get business liability insurance in the USA. Their concept involves teenagers and young adults providing services to individuals on a for hire and on demand basis. The site acts like a middle man and does vet the workers.

They have been trying to secure insurance for the website to protect in case a user brings a claim against the company (e.g. a person is robbed by an individual hired through the site).

They have been turned down by a handful of underwriters, with one company noting that there is too much risk associated with the age group of potential users.

How have you seen other start-ups handle liability insurance?

I don't see that their business model is much different than sites in operation, except that it's a brand new service.

Are you aware of any companies or resources that may help in overcoming this barrier of getting liability insurance for startups?