A bit misleading in the poll question. If done wrong, cloud hosting can be a nightmare as well. It can't guarantee 100% uptime. Maybe in future when it's more seasoned, but not now. When Rackspace Cloud was Mosso, it had some serious downtime problems for quite a while. They have a private customer forum and if you have permissions to view the threads (means you have to be a customer of theirs), you can see the archive of all the complaints back then. Though it seems
good enough now but there are still some speed / responsiveness problems.
Not saying that you can't be good in cloud hosting because they can't, but cloud hosting itself can't guarantee 100% uptime, that's all.