Here's an interesting post from ActiveState's Jan Dubois on running Bugzilla on their Stackato PaaS. It's not a quite as simple as running on your own server, but Dubois does a good job of explaining the steps.
The process Dubois outlines includes:
Short and simple, right? At least Dubois put everything up on GitHub that you'd need to run Bugzilla on Stackato if you like.
One of the reasons I find Dubois' post interesting is how much more complicated it is right now to deploy a fairly standard FOSS application on a PaaS. If you want to run an entire image (operating system and all) it's easy to deploy a lot of stock applications on IaaS providers like AWS right now. But if you want to just deploy on top of a PaaS, there's a lot of lifting to do.
I think in 2012 we'll see smart PaaS providers working with popular FOSS projects to make sure that their software just runs.