The one thing to know about cheap consumer cloud backup solutions like CrashPlan and Backblaze is that they only have one copy of your data. So if their RAID array where your data is stored dies and cannot be rebuilt, it's all gone. You can Google for a few disaster stories about both companies.
Like I said, they are only one third of my backup strategy. My house burning down, or someone breaking in and going into my attic to steal my 30kg 4U server, should be the only two realistic scenarios in which I will need to rely on CrashPlan.
I do same, but in reverse. I use cloud servers, with versioning backups, but still beam additonal backups back to office. Just to survive total data center destruction disaster.
Backblaze doesn't use RAID, they use blob-level replication. I'm sure they can lose data, the question is how likely they are to lose data simultaneous with you losing your HD and local backup.
Ideally in most circumstances you should have at least one cold (non-raid, non-connected) backup of all data, and an offsite one. More being much better.
