In my book Node Web Development (see sidebar), I spent the first chapter trying to sell the reader on using JavaScript on the server.  That's because the typical server side languages do not include JavaScript, meaning everyone has to be scratching their head and wondering why they should use JS on the server.  I suggested that, theoretically, one big win will come because the front end coding and back end coding will both be in the same language, JavaScript, which will make it possible for front engineers to talk with server engineers in the same language.  Or perhaps even be the same person.