One of the most common objections to libertarianism, right after “but who would fund the roads?”, is “wouldn’t a private fire department leave your house to burn if you hadn’t paid?” Here is a very long investigation by someone who has investigated the history of private fire departments and says that - at least in early modern England - the answer was no. I don’t want to argue with this detailed historical scholarship, but I notice I am confused - if the private fire department would save your house whether or not you paid, what was the incentive to pay? [update: see here for answer, the companies sold fire insurance]. Related: government fire department lets man’s house burn because he hadn’t paid a $75 fee, and there was no procedure for allowing him to pay on the spot.Emphasis mine, and here's the link about the incident in question. I found this amusing, because Andrew Koppelman made a big deal out of this event as if it were a black mark upon libertarianism in his book Burning Down the House. (My earlier posts on his book are available here and here.) I think Scott Alexander's reaction is what a normal person would think if they'd heard this story without any explicit prompting that it reflects on free markets or libertarianism. (I don't see any reference to Koppelman or his book in the comments, so as far as I can tell this is an unprompted reaction to the story.) Alexander has dismissed Koppelman's thesis, without intending to or even knowing that he did so.
If you don't know about the story, this was a government fire department, refusing to service a house in an area that previously got no fire department services at all. This is more a reflection of the DMV model of customer service than it is or untrammeled free markets. It is typically governments that decline to provide service even when there is an obvious deal to be made that would benefit both parties. In contrast, markets usually find a way.