Paul has written a nice blog on cloud nativity.
Well what is it? When a new technology come around, you can use it, but it is possible that you are only using it to handle your old usecase. Often, new technologies comes with new strengths and powerful features. To get best out of it, you should be using all its strengths, not just implementing your old scenario.
Lets try to be concrete. With cloud, you can move your apps to the cloud, and you might get some benefits through economic's of scale as your computing provider might be able to give you computing power cheaper than you running your servers. But still there may be lot of other potential benefits of the cloud you are not getting, like elasticity etc. It is like, if I buy a iPhone and only use it to make calls, even though it is cools and it covers my old usecase---making calls---I am getting only 10% of what iPhone can give me. So in the same way, if you are going to use the cloud, you have to look beyond your current usecase and be aware of wonderful new scenarios cloud can enable. On the flip side, if you go around telling "I brought a iPhone, but call quality is the same", obviously you are off the mark by a lot.
On his blog Paul is trying to define some of features required by middleware if it is to exact the best out of cloud on your behalf. They are Distributed / dynamically wired, Elastic, Multi-tenant, Self-service, Granularly metered and billed, and Incrementally deployed and tested. Refer to Paul's blog for more details.