The important thing is not just to backup, but also to use your own domain name. Your following will have a difficult time re-connecting, if you have to replace your address from yourname.hostedservice.com

Whereas when you control your domain name, all it takes is a DNS change, a few hours, and your backup can be restored elsewhere. You keep your following, and all is well.

This is why I moved back to blogging on my own site, rather than microblogging elsewhere. If it's worth saying, it's worth writing a real article about - on a site I really own and control.