Earlier quoted context omitted.
> Google and Amazon invested in them for their own businesses and are now productizing the 'remainders' This is a myth. Both companies created their infrastructure businesses as separate entities by leveraging their datacenter expertise, but they were not 'remainders'.
Very interesting, this doesn't match my experience, can you say more about how you reason to the claim that Google created a separate 'infrastructure business entity' ?
The only way the business model of selling spare resources could work is if you found customers with a different usage pattern to fill the trough. That's hard.
Yes, you can find some customers with time-insensitive batch processing that could be done during the night time. But Google and Amazon already do massive amounts of batch processing, and still won't have a flat utilization level over the day.
Or alternatively you could try to flatten out the diurnal variations by making sure there's no geographic affinity between users and the DCs. But that's suboptimal given intercontinental network latencies.