application using bookmarklets?

Hi all

On another subject entirely...

Is anyone doing (or interested in doing) a application that lets 'anyone say 
anything about anything' and offer a bookmarklet that lets people surf around 
seeing what people said?  

The back end seems to me like it would be a good test app for some semweb 
technologies, mainly storing lots of simple RDF data + keeping trust web data 
for the users.   In particular writing a user interface to choose namespace 
for assertions and communicate possibilities to not-very-technical users 
would be a good exercise, I think.

Is this kind of thing done somewhere already?  

Thanks

--Golda