I would like to have one VM for off network developments or document editing where I can ensure viruses, spyware or trojans are unable to contaminate the system.

I would like a VM for web surfing, where I could easily throw away the VM and restart with a fresh one. Same for mail or other internet applications.

I would also like to have one VM dedicated to do security sensitive tasks like monitoring my bank accounts and so.

Now browsing reddit can result in installing a trojan or whatever that puts all my applications in danger.

Pushing this logic a bit further, we can see that the logic is to go for a more lightweight desktop with eventually more smartness on the remote service than today. But also to combine multiple OS on a same machine. Such systems would work as well on lightweight hand held devices as on big PC with 128 CPUs.