While I do realize that "the cloud" is really just a buzzword for "hosted on the internet", I'm still proud to announce that my personal WordPress sites are now all hosted on Windows Azure.
I've been really impressed with the overall simplicity of getting a WordPress multisite up-and-running, as well as how the performance has been compared to my last host. As an added bonus (if I calculated correctly), I'll be saving $5 a month in hosting fees by using Azure (Windows Azure Web Sites, Blob Storage, and ClearDb).
If you're currently running a WordPress site on a shared host, I'd highly recommend looking into Azure. Besides a decent price and good performance, their git-based deployment setup is stellar. Seriously, check it out!