What I'm arguing is that the trade off is key-value vs. MySQL for small companies. They pick their path at that point. If you go with RDBMS then you might end up at Oracle at some point. If you go with key-value then I guess you stay there.
If you've gone with key-value it's because you've decided that you don't need RDBMS features.
I'm just wondering about those cases where lots of data is stored in RDBMS which could have been stored in key-value storage engines as well. And with the increased query capabilities of k-v engines the no-mans-land is getting thinner.
The incentive to switch is equal to the license fee - the cost of the switch.
And possibly the convenience of being able to use cheap non-specialist hardware.
For the majority of the companies out there the cloud is still more expensive (and more risky, and privacy sensitive) than storing it on their own infrastructure.
But there are solutions in that space as well, having your own on-site 'private cloud', using all of the infrastructural tricks of cloud computing without the loss of control or the service premium.
For many big businesses I think that makes good sense.
If you've gone with key-value it's because you've decided that you don't need RDBMS features.