A strange set of arguments if only that we don't make them for any other enterprise platform or application. Windows, for instances doesn't easily port or play with Linux or Unix. So we've never really expected that kind of portability. Android and iOS are also good examples of the siloed nature of platforms.
To suggest that portability or vendor independence is possible is an interesting way of constraining the Cloud. However, we do have VMWare but it isn't open source.
Hopefully it will happen in our lifetime.
Thanks to David S. Linthicum and SearchCloudComputing
Three questions that can make any open source cloud vendor squirm