Web based architecting tool for everyone

Of late I am thinking of a web based architecting tool in the lines of Google Docs .

This tool shall be targeted to the technical community as it shall have a mind map integrated in it .

Features I am thinking of presently
1) Online collaboration feature
2) User tracking with notes to see who has made the change
3) UI with Silverlight

Need to think of what technology to use for the web applicaton.

I personally see Mind Map as a great tool, becuase it gives way to expressing ones thought process .

I prefer Mind Map for following reasons :-

a) Thought processes range from freshers to CTO’s .
b) No syntax/idoms to follow – users can represent their thought pictorially.

Dont know how long with this project take , but I think if I can make out it shall have a far reaching effect across the world.