Web marketplaces are perhaps the best business model ever. This chart, from BVP, shows 500 current vertical marketplaces.

More info from BVP’s Jeremy Levine:

http://techcrunch.com/2015/04/10/as-vertical-marketplaces-rise-craigslist-faces-its-demise/

http://www.bvp.com/blog/emergence-end-end-marketplace

http://www.bvp.com/blog/no-horizontal-space-why-internet-spawning-vertical-marketplaces