I have an iPhone 5C and have logged out of iCloud (in order to test in App Purchasing on an App under development).
The 'phone indicated "Removing iCloud data...", which seems reasonable, but it has been stuck like that for around 30 minutes now, which does not. There is not that much iCloud data on the 'phone.
Pressing Home closes settings and other apps can be run. But the logout process does not appear to be complete as the In App Purchase test does not ask for an account name, just a password. Reopening Settings just brings back the "Removing iCloud data..." indication.