And so a brave new world of utility computing markets makes another step with AppDrop, a "proof-of-concept to show that Google's App Engine platform can be ported to other hosts"
Read more about it at Chris Anderson's blog. There is also a write-up by Andy Baio.
N.B. I said starts because this isn't true portability or an example of a competitive market. This is just another step heading in the right direction.
