Ask HN: Creating a user-generated review site. Thoughts?

I am building a site where users from a niche demographic can review products and services targeted at them. Businesses, in turn, can claim their page, respond to reviews and manage their reputation.

I'm just starting and would really welcome any insights, advice and or reactions on the points below. Most of what I hear is that by getting into this I'm facing an uphill battle bigger than the one faced by most product/service based startups. :)

1. Solving the chicken-and-egg problems that review sites face (similar to marketplaces). I thought I could build a directory of products and services and the proceed to attract users/reviewers. Lastly, I would contact businesses to 'claim' their product site.

2. Possible revenue models for such a platform. I'm considering keyword-based ads (without collecting private info) and charging businesses to add features to their individual product sites.

3. How to determine product/market fit. This seems 'easier' with a concrete product or service, but not so much with a review platform. I guess marketplaces face the same problem. Struggling here.

Thank you.