Blogging platforms that you pay for hosting your blog, like wordpress.com, write.as, ghost.org (not sure about popups there). The best assurance regarding future changes is always using your own domain, so that you can use it with a different platform in the future.

While self-hosting isn’t as easy as posting on Twitter, it isn’t exactly hard either. You can also pay a service to do it for you, like bluehost.com for wordpress.org instances.