Real conversations are great, but terrible for anyone not in them. What if a co-worker is out sick? At lunch? On vacation? Without studious note-taking any ad hoc conversation is just an untracked change. Not saying they shouldn't occur but if they do, the change (if any) needs to be appropriately communicated to the rest of the group.

I've found that note-taking / decision communication happens so infrequently that it's far better in the long run to just stick to logged forms of communication.

If it's a pair programming team, of course, the documentation is in the code. But if it's something architectural or changing the direction of the product/team, it's gotta be written down.