Should programmers who build websites/web applications understand cryptography? I have no idea how most crypographic algorithms work, and I really don't understand the differences between md5/des/aes/etc. Have any of you found any need for an in-depth understanding of cryptography?

I haven't needed it, but I wonder if perhaps I'm missing something. I've used salt + md5 hash to encrypt passwords, and I tell webservers to use SSL. Beyond that, I can't say I've used much else, nor can I say with any certainty how secure these methods are. I only use them because other people claim they are safe.

Have you ever found a need to use cryptography in web programming aside from these two simple examples?