Do you even need a Website?
Facebook can host any content you want, from your community to rich media. It can even host and manage your e-commerce. Similarly, Amazon marketplace lets you build multi-page profiles and e-commerce stores. Get a nice vanity URL and set up a redirect and you’re all set. Need more functionality link to a Tumblr account. Right?
It depends on what kind of organization you’re trying to build. Today it’s not uncommon to start a temporary or seasonal company. Jump on a trend, milk it, close shop and move on to the next thing. I actually know a lot of people whose business model works like that. Think food trucks, some app developers and pop-up stores. For these people, “sharecropping” on social networks and 3rd party platforms makes sense. It’s cost-effective, you can build an audience quickly and they’re easy to manage (but difficult to manage well). The downside is you are at the mercy of that platform.
If Facebook changes its tab size or eliminates Facebook Marketplace, the business could become inoperable. If you are similarly dependent on Amazon, and they decide to take a bigger chunk, you may be forced to close the door. If you have a temporary business model you’re fine, but if the long-term goal is to build a business that lasts then you need to be your own landlord. For long-term security, use social networks and third party services as a way to improve and grow your business, but not as your primary place of business.