They can also affect the long-term value of a website. Make them refer to only one thing Good URLs are like the great pyramids. Minimalistic and built to last for eternity. Make Them Short Long URLs break more often than short ones. Long URLs are a big usability problem for novice net-users, and even for experienced users they're very irritating to deal with.
Brevity is gold.
Nonetheless, human readability helps tremendously. An URL is often the only piece of information available to the user about a resource. Cases include URLs printed on paper, on television screens, in e-mail, etc. In these cases human readable URLs help the user decide whether or not to click. Human readablility lowers the mental click-threshold.