Cloud is the new buzzword, and as Bryon mentioned, it was thought to be the end all be all solutionfor many with regards to redundancy and security. As proven by T-Mobile and Microsoft (among others) a simple mistake on a software upgrade deleted MILLIONS of user's data. Not cool.

Cloud is very similar to Clustered except instead of clustering in one data center and load balancing, you're using multiple servers throughout the world (ideally).

Definitely more expensive if you're running any type of application that is popular, and it's also pretty difficult for people with online stores. Databases still seem to have an issue with Cloud Hosting, but it's great for static sites.

Cloud is still very new, and it has a long way to go, but steps are being made and I think that's good - we'll just need to wait and see what happens.

Standard Shared Hosting will not be disappearing any time soon.