Informal / breakout / round-table sessions

At Drupalcon Paris there were two sponsored rooms "intentionally left empty", that people could book informally using a whiteboard down in the foyer. I think this worked really well, and meant that there was plenty of slack for people to organize things they felt were necessary at the time, but couldn't be planned beforehand: tutorials, specialist discussions etc.

Will something like this be available at DC CPH, outside of the unconference day? What do other people think? Are informal spaces a good use of the conference venue? Is there a risk that groups will feel disenfranchised if they can't have these spontaneous meetings?

(I'd really like to facilitate - not exclusively run - an interactive session for Drupalistas working in or for the NGO sector at DC CPH. I don't really want to book a session and end up with the expectation that I'm meant to give a talk: I don't think that will help the people - like me - I want to help.)