First we had communication networks, like telephones and email. Then we had social networks, like Facebook and LinkedIn. Now we have market networks, like HoneyBook, AngelList, Houzz, DotLoop and Joist.
You can imagine a market network for every industry where professionals are not interchangeable: law, travel, real estate, media production, architecture, investment banking, personal finance, construction, management consulting and more. Each market network will have different attributes that make it work in each vertical, but the principles will remain the same.