[999900000999]

Unless you have a really good reason to, stick to a few programming languages.

Hypothetically let's say F# Guru gets hired. They're the only ones who really knows it. They program a key system in it, then quit.

Who maintains all this F# code.

[jamesfinlayson]

Agreed - I worked for a company that had no restrictions so there was Java, C#, C++, Python, JavaScript, TypeScript, CoffeeScript, Go, Ruby, Scala, Lua for various different bits and pieces (as well as some more esoteric stuff like a niche database that there very few developers for). I think things kind of worked because the different choices were restricted to very siloed teams but... hardly ideal.