I looked at some of these services about a year ago and realised that for the amount of data I have they just weren't practical. My image files are approaching the 2TB mark. My internet connection has a slow upload speed, significantly slower than the download speed. If I was lucky then uploading about 8GB per day might be possible. Therefore it would take nearly 9 months, assuming I stopped taking any more images. I took almost 9GB of new images on Saturday and am shooting tonight and expect to take maybe 3GB more. That's another day and a bit of uploading. Long before that would complete I would get emails from my ISP warning me about overload their systems.
Assuming I'd got everything uploaded and my storage went pear-shaped it would then take me around a month to download everything back - plus more warning emails!
So unless your data volume is significantly less or you have a much fast internet connection than I do the practicalities of it might just rule it out.
There was one service that allowed you to send in a hard drive as a starting position which would get you up and running a lot quicker.
I've just found the following link which is a review of various online backup providers. It's a couple of years old and written from a Mac perspective but does plenty of good advice. It does mention Backblaze so the fact they are still around now is good news - http://www.macworld.com/article/142606/2009/09/online_backup.html