It's worth noting that even functional programmers will admit that stack traces are sometimes useful. People have even done research into capturing useful stack traces stack traces in the presence of tail recursion:<p><a href="http://libra.msra.cn/Publication/13279173/finding-the-needle-stack-traces-for-ghc" rel="nofollow">http://libra.msra.cn/Publication/13279173/finding-the-needle...</a>