"If I can't see something actively fall, then it's not effected by gravity."
Unsurprisingly, I fall into the "it's negotiation" side of this debate. Negotiation that happens prior to play - e.g., rules, social contract, etc. - that binds how play processes unfold still strikes me as negotiation, even if it's implicit. It's essentially the code of conduct, terms of service, and social contract of play. Just because we only notice the negotiation during moments of friction, doesn't mean it's not happening constantly.