How reliable do you consider USB Thumb Drives to be?

So why would you be discussing it in a topic explicitly and entirely about USB flash drives? Complete left turn, apparently.

ETA: I know about backup services. Which is why I was asking about what they have to do with flash drives. Which is the topic of this discussion. Hence my question. I was afraid I was missing the point. Turns out it wasn’t me.

Well, the subject of the discussion in the OP is flash drives and backups, since he wants to use USB thumb drives as a backup and is asking if that’s reasonable. Suggesting other reasonable (and easier) methods of backup seems on-topic to me.

I’m using Backblaze… Any strong opinions on their reliability and reputation?