I think the language debate comes down to two classes of people: (1) people who care passionately about languages and code aesthetics, and (2) people who don't really care. Unfortunately, the second class of people are more unified and comprise at least a plurality, so they win.

The problem with the first camp is that we all want to use different languages-- Haskell, ML, Clojure, Scala. And these are all good languages! But companies can't afford to have more languages than there are people, not as the latter number grows and as being able to read code becomes more important than being able to write it. So every company needs to limit its white list. Those of us who are passionate about good languages nonetheless disagree on which of those good language to use. And we do ourselves a disservice when we bash Python because it sucks compared to Haskell; the result of this disagreement is we end up having to use C++ or Java.

The perversion here is that the reason so many companies coerce their codebases to C++ (i.e. limiting the whitelist) is that they recognize the importance of reading code. Yet they choose languages (C++, Java) where reading average (not bad code, mind you, but 50th-percentile code in a production system) code is extremely difficult. A good C++ programmer can write eventually comprehensible, but not beautiful code; a bad or average one can easily make an illegible and unmaintainable mess. For contrast, a good ML programmer can write beautiful, easy-to-read code while bad ML programmers are practically non-existent because they can't get their code to compile. For bad programmers, ML is that evil little language that caused them to nearly flunk that PL course they had to take in college.

What I wonder is how Yahoo managed to get people of sufficient talent to do the project. It seems like one of those hard-but-shitty projects that never succeeds because the people who are competent enough to do it have better options. Do-the-same-thing rewrites are never popular projects, and most people who understand Lisp are not going to be happy about taking on such a project for the sake of C++.

(No, I'm not saying that there aren't good programmers who use C++. There are great programmers who use C++. That said, someone who understands functional programming well enough to read Lisp is not likely to be among them; people who understand FP want to use it.)