Hosting wise I couldn't add much to the above, namely we've dabbled but again there isn't a big rush to promote it just yet. From a programmer standpoint people have been using cloud computing and more commonly virtual computing long before it started within hosting for the use of testing. Though personally I doubt many would ever go as far as to use servers from a third party, mainly as software details of which in the wrong hands could damage said company far more so than managing their own internal servers in a cloud or virtual environment which is the current defacto.

Otherwise as per Conor's example there is little difference between cloud and traditional techniques.