I agree. Essentially it boils down to whether communication protocols and formats are open enough and replaceable with reasonable effort. But with single point

I agree. Essentially it boils down to whether communication protocols and formats are open enough and replaceable with reasonable effort. But with single point of failure, I don't mean outages. I mean, is it open and transparent enough towards your endpoints, that you can easily replace and / or fix things. Vendors go out of business or even a larger issue: your business changes.