Backblaze has no limitations on the amount of data you can backup or the speed at which you can backup. You can read a bit more about this on our blog: http://blog.backblaze.com/2011/02/03/backblaze-is-committed-...

Gleb Budman CEO, Backblaze

I made the Mozy to Backblaze jump a few days after Mozy thanked me for being an early adopter by quintupling my bill. I only had about 250GB to back up, computer was on 24 hours, I throttled it a bit during evening hours to not interfere with Netflix, and it was about three weeks to finish the backup. I don't know if they have a graduated scale if you have to back up a lot more.

So far, I'm very happy, but I haven't had to restore yet...

I don't know either, but, I made the switch from Mozy to Backblaze (after their CEO told me via e-mail that they won't jack up the pricing), and I've been happy. (like other commenter, I haven't had to restore yet - aside from some tests)

I backed up about 600 gigs to Backblaze in about 3 weeks