Whether FB wants to call it hackathons, hack-a-tack, tick-hack-toe doesn't matter.
But the message from the parent here is that it's cool to build a product by pulling one-nighter. (And we all know that's the culture in Facebook).
The same theme again and again that sort of... screw our industry as a whole: romanticizing the notion of hacker.
On the other hand, I don't think FB Chat was written in one-night.
Hackathons are great for prototyping ideas/products/proof of concepts. Engineering is essential for building large/stable/scalable systems. Clearly Facebook is good at both.
I like to think of myself as both a hacker and an engineer. Neither word describes what I do completely.