There are a lot of things that can screw up a blog or leave it inaccessible–hackers, server meltdowns, or bad hosting companies among them. If you’ve put time, energy, and money into building a blog, there are two articles which will help you protect it better:
In the event that you and your host have a disagreement and they shut down your account or site, registering your domains somewhere else will help you move your site faster. See the article for more details.
WordPress has two parts–files which provide the structure/theme/plugins/etc and a database which stores all the posts/pages/comments/settings. The article includes plugins you can use to backup each part and information on an alternative method of backing up your files.
Even if you don’t want to go through the hassle of doing #1, consider doing #2 today. If you’re used to installing plugins, it should take you less than 20 minutes to make your blog a lot safer.
(note: if you’re blogging at WordPress.com or blogger, you don’t have these options. Consider setting up a weekly reminder to use their export function to export a backup copy of your blog.)