For almost a year now I have been using CrashPlan+ as my online/offsite backup solution. One of the key advantages behind CrashPlan as compared to many other online backup services is the fact that it offers unlimited backup for a relatively modest fee. Mozy, another service that I once used, used to offered unlimited backup for a flat fee as well, but it discontinued this service in early 2011. With CrashPlan+ I am able to store upwards of 3 TB of photos (including scans of film and slides belonging to my grandparents and going back decades), home movies, PDFs, documents and other data for $119.00 per year. By contrast, to store the same amount of information with the Amazon S3 service (another backup service where you must pay by the GB) would cost $4,792.32 per year (according to this calculator), which is somewhat beyond my budget, to say the least.
Of course, Amazon S3 is a professional-grade service, whereas CrashPlan+ is intended for consumers, so it may not be fair to compare them directly. One of the sacrifices of using a consumer service is being restricted to slow upload speeds. Indeed, though I was able to physically send the first 1 TB of my backup on a Lacie external hard drive to CrashPlan for a small additional fee at the end of last year, I have been spending the last 9 months finishing the upload of the rest of the 2 TB over the Internet. Granted, the slow, gradual initial upload is not just the fault of CrashPlan. I am using a fairly average Cox cable broadband subscription that permits me to transfer only 200 GB per month. (However, I should note that the author of another review had an even fancier Internet connection allowing up upload speeds of up to 100 mbps, and yet CrashPlan restricted him to upload speeds to no more than 3 mbps).
I have generally been happy with CrashPlan+'s performance in allowing me to restore files. Though I have not had occasion to request large chunks of my data back (I have on-site Time Machine backups on a Drobo that I have been relying on for that), I have been able to restore individual files from the cloud with ease. CrashPlan claims to keep unlimited versions of my files going back to the first backup, and I have used this feature to find older edits of files that my local Time Machine archive seems to have missed. This has been immensely convenient. However, I do notice that from time to time I cannot access CrashPlan's servers on demand. Sometimes I have had to wait an hour or so before being able to login and find my files. Apparently, around-the-clock access to data is not a guaranteed feature.
I have also been concerned by the accusations of others online that CrashPlan has lost their files. Note, for example, this review that shows up on the first page of Google results for "CrashPlan". The person here lost data due to "human error" at one of the company's data centers in Minneapolis. However, apparently this was an isolated incident, and now measures are in place to prevent anything similar from happening in the future.
I would hope this is true, because currently there is nothing that matches CrashPlan's price point and the unlimited backup. I also do feel some assurance in the fact that even if I cannot practically re-download all of my data in case I lose all access to physical copies of my information, I can pay to have the data sent back to me on hard drives (the "Restore to your Door" service).
In any case, CrashPlan is far from being my only backup solution since I do have local backup. When it comes to data backup, there is security in the number of copies you make and the diversity of backup solutions you use. Indeed, in the world of library science, there is a offsite digital preservation platform entitled LOCKSS, or "Lots of Copies Keeps Stuff Safe", which is certainly a principle born out by historical experience. Information that has been kept in one library or one place has been much more likely to perish due to man-made or natural causes (note the fire that destroyed the Library of Alexandria), whereas information that is disseminated to multiple places has a much higher chance of survival (note what the printing press was able to do for the dissemination of Martin Luther's translation of the Bible, which, if it existed in only one copy, could have easily been seized by the Catholic Church and destroyed).