At Machine Zone, we've been using formal methods to specify and verify systems we have in development. This is something we've only been doing in the last 6-9 months though.
It does seem like online gaming companies are at the forefront of distributed systems implementation. See League of Legends' use of conflict-free replicated data types, for example: http://highscalability.com/blog/2014/10/13/how-league-of-leg...