Facebook had one of the most insane Product Market Fits in the history of humanity.

Building @kiwi 
Writing @ https://kanfa.macbudkowski.com/

It was crazy sticky. It is worth noting though (imo) that the Facebook app wasn’t the product - user data and ad space were. The app was a crucial part of a product strategy for capturing commercial market share. 

Ofc this statement hinges upon “product” defined as a good or service customers pay for.

a jiraffe on the internet • nf.td/morereese

I'd say it was a double-sided product: one product for consumers, another one for ad buyers :)