Question: I develop asp.net websites, and I read about cloud computing, windows azure, etc. But in the end, I cannot see any pratical reasons to change/move/etc my services to the "cloud".   
What the benefices?

Cloud computing is some kind of "evolution" of web farms?

Thanks, and sorry my ignorance....

Answer: 
To explain the benefits, I'll use two examples [Microsoft Azure](http://www.azure.com) and [Amazon EC2](http://aws.amazon.com).

In the case of Amazon EC2 you can rent a virtual image with Windows Server 2003 and SQL Server for a few cents per machine per hour. Like other hosting companies you don't need to manage the hardware yourself; your machine is stored in Amazon's datacenters and they'll make sure the server's always up and the data backed up, etc. You also receive an API so that you can automatically spin up new instances of the machine to cope with fluctuations in demand.

Azure takes this a step further - you don't need to manage your system. Using the developer tools you create your ASP.NET website and provide some metadata to indicate how your app is split into front end and back end, and then you choose how many instances you want and click "deploy to Azure". Microsoft again takes care of making sure the app keeps running, is geographically distributed, etc. In fact you never know which computer your app is on or even how many computers it is spread across. Microsoft also provide several web APIs that you can call from your Azure app for things like authentication and storage.

You can find more info on the web sites given above.
The short answer is that "the cloud" is a buzzword for virtual server services. If you need to use it it's because you don't want to spend your money on IT-staff and servers that can do the same thing.

Azure has some extra features for microsoft developers and you can watch the [PDC 2008 keynote](http://channel9.msdn.com/pdc2008/KYN01/) where they introduce Azure that talks a lot about it.