Is there a collaboration tool example in silverlight or WPF for multi user? (like google docs but not that complex)

Question

We are designing a C# product which involves multiple users accessing common piece of data.

In short something like google docs but not that complex. Is There any good example for architecture or design to follow, read, understand.

And adding to the complexity, user can belong to different geographical location. ( is distributed database the right way, database replication, centralized database?)

Kindly advise.