These services store your data on the service provider's drives. You access your data over the Internet. For increased security, they typically store your data at multiple locations. The services generally provide software for file encryption to keep your data secure, and for scheduling automated, incremental backups. Most offer remote file sharing. Because your data isn't on your premises, it's safe from burglary or natural disaster such as fire or flood. And there's nothing to break or lose, you can add or subtract storage space as needed (sometimes at extra cost), and your backups are available anywhere over the Internet. But you must be comfortable entrusting your data to a third party.
Initial online backups are excruciatingly slow. In our tests it took more than 24 hours to upload 9GB of test data. With 25GB of data, an initial backup can take several days. Consider leaving your computer powered on for the entire initial backup. Subsequent backups are much quicker, because they involve only files that have changed. Factors that affect backup speed include file type (for example, photos typically take longer than text documents), computer, connection speed, your computer's other activities during the backup, and network traffic on your end and at the online service.
If you have lots of digital images, consider a photo-sharing service, which lets people you invite view and print photos. Uploading will still be slow, though. And be aware that some sites, including Kodak Gallery and HP Snapfish, now delete your images unless you make a purchase within a certain timeframe. One service that has promised not to do this is Shutterfly. Make sure you read any site's terms and conditions before you sign on.