Online backup systems for the Mac already exist -- Mozy and Crash Plan for example. Backblaze is a bit different, because it is designed by default to be used without configuration. Instead of having to manually choose what types of files or what specific folders you want to backup, Backblaze will just back everything up -- with the exception of your OS and your applications. You can add exceptions and limit what is backed up by playing with the preferences, but by default, Backblaze is set to back everything up.
Setting Backblaze up is dead simple. You just install the program (by default it will run in the background, though you can change this), enter in your e-mail address and password, and it will start backing up your files. The default setting has Backblaze running any time it finds an available internet conenction. The backup process is constant and Backblaze stores multiple versions of a file for 30 days (so if you are frequently changing a document or spreadsheet, 30 days worth of revisions are saved to Backblaze).
If you want more control over how Backblaze runs and what it backs up, you can access those settings in System Preferences where Backblaze has an entry. Here, you can choose to only run Backblaze when you decide; once a day, or continuously. You can also adjust the throttle of the backup speed. In exclusions, you can add folders or file types to the exclusion list. The base Backblaze exclusion list for file types and folders cannot be changed -- and while I'd say 95% of users won't need to backup these files or folders, this is something for power users to be aware of.
One nice thing is that the individual user Library folder is not excluded from backup. While I use Time Machine, I find it much more effective for my purposes to just backup my user folder when I need to reformat my system. Backblaze backs up the user library. The maximum file size is 4 GB, though you can lower this if you want to exclude really large files from your backups.
You can also backup connected external drives. Networked drive support isn't available right now (though they are working on it), but you can add external drives to your backup preferences either when you start to configure Backblaze or later on in System Preferences. This is really nice if you always have a USB or Firewire drive connected to your Mac.
I found Backblaze to be pretty fast, though I went ahead and upped the default throttle settings a bit to do faster uploads. I didn't notice any major hindrance to my download speeds or regular web access, though pausing the service while downloading or sending a large file or streaming video might be a good idea, depending on your connection.
By default, all uploads are encrypted using AES "military grade encryption" over SSL. You can also choose to set yor own encryption key that Backblaze will NOT store. This will be required in addition to your e-mail and password for retrieving your files, so if you choose to privately encrypt, either use a key you won't forget or write it down and keep it in a safe place.
I think that one of the most overlooked aspects of online backup systems is the restore process. Yes, you want the backups to work -- but being able to access your files in the event of disaster is just as important. My biggest problem with Mozy is the amount of time it takes to get files. In my experiences, it takes several hours for the archived file to be ready for download and then piecing them together is kind of a chore. That process might have improved in the last six months -- I don't know -- but it was enough for me to not want to use it for any large backups.
Backblaze actually has some pretty robust restore options. You can login to your account and view all of your backed up files online, select the files or folders you want to download and then you'll be e-mailed when a zip file is ready. In my tests, it took under 5 minutes for me to receive an e-mail message and the 120 MB test directory (compressed to 55 megs) downloaded at almost 1 MB a second on my cable connection. The entire directory and hidden file structure was maintained exactly as it is on my compuer.
But most of the time, if you need to go to restore your computer, it's because of a data disaster. Either the hard drive died, the laptop was stolen or some other component died. Downloading 100 GBs of data and then braving a restore isn't the most appealing idea in the world. Thus, Backblaze can send you out your data on DVD or on a USB drive. It's not cheap -- $99 for DVDs, $190 for a 160 GB Western Digital USB hard drive -- but it's not overpriced either. That way, in the event that your computer has been stolen or has just gone kaput, you don't have to wait until you get the new system to start the recovery process. They'll FedEx the drive or discs to your house.
For $5 a month and unlimited storage, Backblaze is a nice, efficient and hassle-free backup solution. The Mac program has a very Mac-like interface, its backup behavior is very similar to Time Machine and the restore process is really, really nice. 300 TUAW readers can sign-up for the beta here and you can try the service out for two weeks and see if it meets your needs.
Seriously though, whether you use an online serive, Time Machine, another program or just diligent weekly backups -- please, backup your computer.