Any one know, is it possible to host Bugzilla application in cloud ?
I guess with "in cloud" you mean at a hosting provider on something like a virtual server. Certainly that is possible. Bugzilla is a server side application that relies on a http server and an smtp server for communication and a relational database in background, all not a problem here. However bugzilla is, unlike typical web applications, implemented mostly in perl (language). That means you have to find a hosting provider offering such environment. That is possible from a technical point of view, but not very common. This is also explained in the documentation.