Most people with multiple TB's of data don't need to send it all up to a backup site because the content is already backed up on hundreds or thousands of systems around the world and they just need to fire up a bittorrent client to download it again.

It took me weeks to send up just my digital photos as I've only got 640Kbit/s upload capacity. Yeah, by 2015 the CRTC says I should have 1Mbit, but it's not proposing that be passed into law or anything.

Even if I had the required transmission rate, I've also got a 120GB per month usage cap. 4TB would take a lot longer if I had to meter it out. Probably over 6 years if I was going to be doing any downloading at all. 2.8 years if I was using up the whole cap for only uploading. Yuk.

I've got probably 100-200 GB of critical data that I'd consider backing up online. That's in addition to the local and offsite backups though.