... wanted with these features (as best available):
1. User upload of pictures, text, audio and video
2. Collection of (1) into Albums by user
3. User annotation of items in (1)
4. Security optional; items password protected for individuals and groups
5. URL?<something> access to items directly (password protection active)
Are there any services which can provide this online now? or must I build my own system?
No need to build your own system... huge amount of work and expertise required.... but hosting your own "Multimedia database system" will not be free either.
Here is an open source application that you might be interested in.... at least review, compare features, etc: http://www.phpmotion.com/
So while the software is more or less "free", you will need a dedicated server to install it on.
Still, you could put up a very dynamic site in short order and have tons of functionality.
Eye for Video