Trello – a popular collaboration tool – allows users to create public boards but users expectedly don't care about interface warnings:
This leads to undesirable consequences like passwords leaks. Just check it by yourself, paste
site:trello.com/b/ password and you will find lots of boards which are used as password storage. Even more you will find if you google
site:trello.com/c/ login password which exposes tasks only:
Cloud definitely has lots of advantages but privacy is not one of them. There is always much more risk that data will be exposed to a third-party in cloud services than in on-premise solution hidden from the outside world in virtual private network.