What happens if/when an issue comes up that the managed service can't/won't resolve? If you can move to another provider that will, you'll have some leverage. But there's always headaches associated with any move/migration and a possibility of lock-in to the provider's platform.

Yes, I certainly agree. One of the major problems with taking an application implemented on a PaaS solution to production scale is that you essentially join at the hip the continued success of your core product to the eventual fate of an outside vendor's platform. What's worse is that by the time you realise you've grown too big for the PaaS you may have to expend a huge amount of engineering effort and customer good will to move off, if you even can. Indeed, PaaS providers will try to make it /easy/ for you to make engineering decisions which lock you into their platforms -- and they will present those choices as helpful at the time, which makes them quite insidious partners.

This is a very valid concern. We are in the early stages of this transformation and naturally winners and losers will emerge as the market becomes more mature and the big guys begin to purchase and consolidate PaaS.

Rewind N years and you can replace PaaS with some other technology that eventually matured and is now considered ubiquitous.

Good point. Two companies I know of (Expensify.com and Trap.it) get around this to a certain degree by hosting on multiple vendors. With that they are better able to account for sudden changes to the market if one goes down or drastically raises their prices.

Above just showing a certification, hosting providers never give access to their data centers.