I like the idea since I started using tags in favour of folders for my very large mailbox.

I can see a few issues around security if anyone can create any tag they like.... could be difficult to protect critical system files.

Maybe it could be secure if it also included namespaces for tags which could be secured.

If we allow this kind of illegal tipoff as evidence to police, then it gives criminals who have the skill to plant fake evidence a very big lever against everyone.

"Hey buddy... look at all the pics I put in My Documents for you. How about you wire me $1000 to my account in so I keep quiet about it"