Ninjamini,
It's not a question of speed, it's the broader questions about privacy, security and reliability. If I back up my personal tax and financial records, there's no way I want that out on the net where someone can potentially hack into it. Plus, how can you trust an offsite storage site that THEY won't have a disk crash and lose your 'backups'. A magnetic platter just isnt a good long term solution for permanent data storage (allthough newer flash based drives are intriguing).
On the reliability front, come back and talk to me when someone can provide 5-nines reliability on any sort of residential communication service. The problem with distributed software models is that you're stuck twiddling your thumbs when the network goes down. Sure, it may work great almost all of the time, but in times of crisis or natural disaster, the fundamental flaws get exposed.
Don't get me wrong, I have no particular affinity for optical drives. I just don't see them going away in the near term. Anyone who packages a computer these days without one is doing it for pure cost savings, regardless of what they may claim.