For about the 4,000th time in the last five years, I tried to sign up for a new Web service, but it wouldn't accept my proposed password. Apparently, the site operators decided that passwords should contain only letters and numbers. Aarrrrgh! This isn't the first time I've seen this idiocy, and it won't be the last. But it should be.

Guidelines on how to construct a strong password almost uniformly recommend using a mixture of upper and lower case letters, numbers, and symbols. Tools for gene...