Cloud Hosting - Hosting on virtual servers(VPS/Cloud Instance/VM), with the ability to scale up as and when needed, and scale down when not needed.
The application should be Cloud ready, to host on Cloud Hosting, or rather to use full benefits of Cloud Hosting.
Is CMS like Wordpress Cloud Hosting ready? Well, you can host central database vm, and scale up/down web serving vms, with a load balancer in front of web.
What factors to scale up/down depends upon what level of automation Cloud Hosting vendors can offer. You can scale up during a weekdays office time or based on detecting high volume traffic instantly or based cpu load on web serving nodes. You can also program your own logic.
So, the questions really comes down to,
- is site compatible/automatable to benefit from Cloud Hosting?
- what is the business impact of not serving site during high traffic?