I think the author has the wrong end of the stick a tad. First off amazon would need to work with VMware to use this plugin, as using unsupported plugins causes issues when getting.. surprisingly enough... support.
Also VCAC (vCloud automationn center) has come build in with an Amazon endpoint for the last few versions anyway, and multiple other endpoints.
To put it another way, if you have the option of two on-site virty controllers, one which can integrate easily with many different compute resources (rackspace, amazon etc), and antoher which only works with one... azure... which are you going to go with!
Lock-in is horrible, more of this please for everyones benifit.
(disclaimer- I work for VMware, but this is personal opinion only)