Wiki-based whiteboard?

I had an idea a while back for using the web to create a limitless ‘whiteboard’ for online brainstorming. Then I thought it would also be for personal use maybe, maybe a space for ‘social graffiti’ like Graffiti Playdo? In fact the concept is pretty extendable/scalable, and cross-market as a wiki-based whiteboard:

1. Personal, professional, educational

>It would be your own personal space – so it’s down to you to police it; the space would include such tools like an eraser etc. Plus you could restrict contributors to mates etc on personal sites. or leave it wide open.

>It would be a business brainstorming tool, allowing collaborative creation and linking of non-linear outputs in an easy to use/easy to access medium.

<It would be an online educational whiteboard, a tool to exchange ideas in a fluid medium.

2. Legal issues
Myself as the provider would then just provide the virtual ‘pen and paper’ thus removing the dangers of legal action. In fact it would be up to the user to find their own server space too to completely avoid that. Perhaps for businesses their would be a hosted version though to enable more control/tighter controls?

3. Basic business model
Both personal and business versions would take advertising; obviously the type of advert would have to very tightly fit the medium etc..

4. Technical functionality
On Graffiti Playdo you are limited by the page, my suggestion is to allow the space to extend outwards, as content is added (not allowing content too far from existing graffiti) – with the possibility of linking up individual/business graffiti sites. Perhaps based on existing wiki tools? Dunno, need to ask a developer on this one.