"[Some users] store multiple terabytes."

They are certainly not a replacement for S3, but could be a substitute for some use cases. Also, they can certainly change their stance at any point, but they are certainly committed to truly unlimited.

http://blog.backblaze.com/2011/02/03/backblaze-is-committed-...

http://blog.backblaze.com/2011/10/26/backblaze-2-0-unlimitin...