cnn.com’s URL looks like it’s more for cosmetics than actual function. I know that when I have that URL in my address bar that I’m looking at September 11th, 2004 weather information.
Simple URLS are also easier to remember. You don’t always have your favorites or bookmarks handy (though things like furl make this easier). That’s why those URL shrink sites are more popular. They take an insanely long and complex URL and shorten it into something that’s somewhat easier to remember.