I'm not one to dictate how technologies like these are to be used, but all I can say is that in the almost two years I've been working on Webstrates – a collaborative system using a very similar technology – this has not been an issue.
But surely, if you allow malicious actors to modify your document, then that's your problem right there.
But surely, if you allow malicious actors to modify your document, then that's your problem right there.