A: A backup is a lot like a spare tire. You don't need them 99% of the time, but when you need one you REALLY need one. There are some free plugins that can backup your files. The best tool on the market for this is Backup Buddy and I would also recommend BackupCreator. You are looking for two things in a backup program.
1. You want a system that will create backups in the background. You can think of this as a "Set it and forget it" approach.
2. You want an easy restore process. If you need to restore a backup, that means (in many cases) you're having a stressful day. You don't want a system that's going to add more stress. This is where Backup Buddy comes into play. It's very easy to reinstall your website (and we mean everything, plugins, images, etc not just the posts and pages). Another great solution is Backup Creator
Both Backup Buddy and Backup Creator have meet the criteria. Backup Buddy has more options regarding where to store your backup file (like Drop Box). Both plugins can backup to Amazon S3, or have your backup emailed to you. Backup Buddy is $75 for two sites, $100 for 10, and $150 for unlimited. BackupCreator is $47 for unlimited sites. In both cases you are expected to renew your purchase (for a discounted price) each year. Think of this as insurance for your website.