I have many layers of redundancy.
I keep my primary copy on my laptop hard drive. I use the backup tool in my Norton 360 antivirus software to make two nightly backups. The first is to an external USB 1TB drive that I have attached to the back of my laptop with velcro. It stays on there permanently. The second is to an on-site Seagate FreeAgent GoFlex unit. This is a wireless device that you can put anywhere in the house. I have mine hidden in a closet so it isn't obvious if there's a break-in. It has 2 2TB drives attached to it, and both our laptops use this device to back up to every night.
In addition to those backups, I also have my files backed up in the cloud. I use
www.crashplan.com, and have their CrashPlan+ Family Unlimited plan, which gives me unlimited online storage for up to 10 computers. I purchased several years of service at once, so the price worked out to be about $6 a month. This is a continuous backup, so as soon as I add or change files on my PC, they start replicating out to the cloud. It took almost a full month for my initial backup to complete, but now that it's finally all out there I feel comfortable that I'm covered even if there's a major incident here in the area. (We live near the ocean, so hurricanes are alway a possibility.)
I also use CrashPlan's software to schedule a monthly backup to a second external hard drive that I keep off site. I'd like to say it's kept in my office (which is the plan), but more likely than not, it's in my car. I'll bring it in and connect it to the laptop to do the backup (when prompted), then put it back in my car when the backup finishes.
In addition to those services that back up all my original files, I also keep copies of many photographs on both PhotoBucket.com and Flickr.com. I pay for the pro plans on both these sites. (I wish I'd looked at SmugMug before paying two years of Flickr because if its ability to block right-clicking, but what's done is done and I'm not paying for a 3rd site.) I have these sites mostly for sharing purposes, but it can be considered another version of a backup. I don't have the original RAW files on here, but there are some fairly-high resolution JPEGs uploaded there.
I like that I have multiple on-site, an off-site, and a cloud backup. I also use two different software packages to perform these backups. Those multiple layers of redundancy should cover me for all situations. (Knock on wood.) Fortunately (or not) we'll always have that picture of what I looked like in my swim suit at Disney World in 2012, no matter what.