That's nonsense. Scala is pretty well known. (Apache Spark, Play Framework, Spray, Akka, Scalding, Kafka, etc...)
As for the web stack: Play, Scalatra, Spray, etc...
It can also use the fairly mature Java libs as well: Jersey, Jetty, etc...
On the other hand, I don't know of any popular projects that are written in Rust, other than what Mozilla is doing with Servo.
I can name companies as well: Twitter, Airbnb, LinkedIn, Gilt, Foursquare, The Guardian, etc...
Github still probably runs mostly on Ruby as well, and for performance, you could use JRuby.
As for the web stack: Play, Scalatra, Spray, etc... It can also use the fairly mature Java libs as well: Jersey, Jetty, etc...
On the other hand, I don't know of any popular projects that are written in Rust, other than what Mozilla is doing with Servo.
I can name companies as well: Twitter, Airbnb, LinkedIn, Gilt, Foursquare, The Guardian, etc...
Github still probably runs mostly on Ruby as well, and for performance, you could use JRuby.