http://www.crashplan.com/
Only one worth considering
Carbonite is one of the worst services there is due to their http://carbonite.custhelp.com/app/answers/detail/a_id/1440/partner/carbonite/default.php
The first 35GB of data can achieve upload speeds of up to 2 mbps (megabits per second).
Between 35GB and 200GB of data, upload speeds can reach up to 512 kbps (kilobits per second).
At 200GB or more of data, upload speeds are limited to around 100 kbps (kilobits per second).
25gb of data storage is incredibly small, not to mention the fact that to access it requires using bandwidth and, with the copyright craze we're having today, potentially (depending on how crazy they want to get) puts things you want to store at the scrutiny of someone else. If your goal is to preserve what's on your OS (using the same hardware) I'd suggest something like Ghost. If what you want is to archive files like music, movies, games, etc., I'd suggest an internal or external hard drive.
Everything you upload (assuming you are using a quality service) is encrypted, so there can be no scrutiny. CrashPlan (and a few others) offer the option to mail you a "seed" drive to take off the initial pain of uploading everything, and also offers an option to mail you a restoration drive which makes restoration less taxing as well.
While I do agree that doing a bare metal backup is a great idea (and free tools like Redo Backup and CloneZilla make it easily obtainable) and doing local backups is important, for those extra-important files, off-site backups are a must. Otherwise you run the risk of a local disaster (theft, fire, flood, tornado, power surge frying parts, stupid relatives, PEBKAC, etc) causing you to lose everything. Some people for some of those (theft) may have bigger issues, but some people do have critical information digital only and others can be localized to just your PC and external drives. Cloud storage is a simple off-site backup so I can understand why some would want it (I'll probably always prefer SFTP)