Only so long as you are able to easily interop one tool from one cloud with the others without major consequences. If that was true, then you can freely mix and match cloud services from different vendors.
Alas, this relies on many things, not the least of which are peering agreements between cloud vendors that do not punish the consumer for using a service on one cloud with services from another.
It is possible to an extent today, but for competitive reasons, cloud companies do not seem to have a built in incentive to collaborate. Perhaps the cost of switching and lock-in will force cloud providers to work together in the long one, else they risk alienating customers, and then lack the ability to capture a larger market.
In other words, competition is good as long as people can realistically take advantage of it. I think cloud vendors have an obligation to see that this competition is encouraged and supported.