I've heard from technical leaders at multiple now well established unicorns how they'd never use postgres or switched from postgres simply because MySQL has a lot more tooling built it and many more people are exposed to its shortcomings at "web scale" so that it's very well known where and when things will break.
Disclaimer, I'm a hardcore Postgres user myself, but I also keep tabs on the other tools.
I've been a hardcore and exclusive Postgres user since 2004. Always rolled my eyes when folks say they use MySQL or moved to it from Postgres. Reading about that bug sent shiver's down my spine. I know no system is bug free, but Postgres is one of those systems that have held up very well for me, and now I'm super paranoid. :-( I guess I understand tho, I moved from BSD to Linux for more tooling.
OTOH, it's important to consider that most places are not and will never be "unicorns", so analyzing things at that scale may not make sense. Just because Facebook managed to make something work doesn't mean that you should follow the same path.
Disclaimer, I'm a hardcore Postgres user myself, but I also keep tabs on the other tools.