Is it possible to patent the functionality of a web or mobile app/platform?

Suppose I was the first one to invent airbnb. Could I patent something like "web/mobile application that enables users to rent out lodging"? Or suppose I was the first one to invent kickstarter. Could I patent something like "web/mobile crowdfunding platform for publishing projects and gathering money from the public for such projects"? Can such apps/platforms be patented? Do companies like airbnb, kickstarter, uber, etc., hold patents on the functionality of their platforms or any other related patents?