When you get to this level of granularity the metaphor really starts to fall apart, but the principle is still there: identify your points of failure, the risk of them failing, and ensure there's a plan B.
Most businesses can treat their domain name as fail-safe. If you have a .com/.org/.net, pay well in advance, and aren't doing anything that's currently illegal in the US, you're not going to lose it unless there's a dramatic political shift that's earthshattering for ~everyone.
On the other hand, social media platforms arbitrarily locking you out is a daily occurrence for tens of thousands of innocent people per day. This isn't just a hypothetical risk, it actually does happen to people and businesses all the time. Even the most law-abiding business should not build their castle in a social media platform.
> On the other hand, social media platforms arbitrarily locking you out is a daily occurrence for tens of thousands of innocent people per day.
If you're at all legit, you don't have to worry about being locked out.
Everyone has to worry about being downranked to oblivion, which is the new normal on most SM sites.
This is not a safe assumption. You're just one crazy person willing to harass the family of whoever runs the registrar away from being 'too difficult to work with' and getting your account nuked. They don't charge enough to stick their neck out for you.