There are at least two case in the Plone control panel where negative values where accepted without validation error where only values larger 0 make sense. I reported at least two issues and both got closed with the comment "why would one do that", "why would one enter negative values"...are you guys serious? If a particular value should larger zero then it should be validated...that's why we have validators...or am I missing the point? As a consequence we should disable all validators and depend on the intelligence of the user to enter valid values only.
Sorry but this had to be said.