Do you backup your databases? If not, you should or you are setting yourself up for a tearful reality. Databases are not 100% stable and are subsceptible to shutting down or being corrupted. Therefore, you should always consider backing up your database (the technical term for this is running cron jobs)
At the very minimum, you should backup your database once a week, eventhough I suggest once a day.
If you use wordpress it comes with an installed plugin (version 2.0 and above) that will send a database dump to your email account regularly.
Some applications, like wordpress, allow provide you with a database backup utility.
If you use other database applications and have cpanel, cpanel allows you to backup your database.
If you use other database applications and do not have cpanel, there are options you can use to back up the database.
1. MyBackup: http://www.tufat.com/s_mybackup_web_dat ... porter.htm (we use this one)
2. http://www.webbasedcron.com/
This is hosted cron job service - $16 a year.
Also, you should always have a backup of your web site files as well.