Yeah, it all depends on what you're trying to do. I'd also wager that Graham et al simply had more fun writing Lisp than any other language, and I grant them the right to do whatever they like. Yahoo presumably bought the product because they found it valuable. If they found that rewriting Lisp in C++ was the only way to get people to work on it, I don't question their business decision, although it does seem like a kind of "now you have two problems" situation. (Personally I find C++ way more difficult than anything I've seen in Lisp.)