At the last JSConf, 370 attendees, ~1000 devices online. You are absolutely right. At a certain density all bets are off. We were pretty close to this point at several points in time. The problem gets much harder with more people.

The blog post is very much not about technical details. Having people who actually care is what really counts. This is all, of course, presented in term of not-for-profit-conf where paying people to get it right is usually not an option.