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: 
I think the number-one reason is the level of dynamic scalability that is offered.  

Then I would say the amount of redundancy, that is typically offered.
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.