Particularly in server environments, where scalability is as important as raw performance, platforms matter.
In the scalability battlefield, I couldn't see any other language than Java as the most accepted, most adapted, most supported dominating programming language. Not C#, not Scala, not Ruby can get even closer in next 5 years or more.
Yammer switched to Java when Scala couldn't meet its needs. Twitter switched from Ruby to Scala before also settling on Java. Reddit rewrote its code in Python. Yahoo Store migrated to C++ and Perl ...