title: What makes a "friendly URL"?
body: <p>I've read a great deal of discussion recently (both on this site and elsewhere) about "friendly URLs" but I'm not sure what exactly makes a URL "friendly" and why we really even care (up to a certain point).  Illustration:</p>
  
  <p>The following is an example of a URL that would be held up by the majority of current web developers as "friendly":</p>
  
  <blockquote>
    <p>www.myblog.com/posts/123/this-is-the-name-of-my-blog-post</p>
  </blockquote>
  
  <p>Whereas this would be considered "unfriendly" (i.e. bad, Neanderthal, ignorant, stupid):</p>
  
  <blockquote>
    <p>www.myblog.com/posts.aspx?id=123</p>
  </blockquote>
  
  <p>My questions:</p>
  
  <ul>
  <li>Doesn't the "friendly" URL contain duplicate identifying information about the blog post in question?  In other words, once you have the id (123) of the post, why do you need the title?  Wouldn't this be a violation of the "don't repeat yourself" mantra?</li>
  <li>What difference does the form of a URL make as far as users are concerned?  Do users ever actually <strong>type</strong> full URLs by hand (other than the TLD, of course)?  Do users ever look to the URL of a page to determine what the page is about?  Why do we need the title of the blog post in the URL?  Isn't that what the page's <code>&lt;title&gt;</code> tag and content are for?</li>
  <li>I often hear SEO as a reason why the "friendly" URL form is preferred.  Why does a search engine spider care about the URL?  Aren't they just automated pieces of software that crawl pages (and the links to other pages that are contained within them)?  If search engines were written like other software components (e.g. database access components), the URL would just be a meaningless identifier (similar to a rowguid in a relational database) to them. If I were designing a database schema with something like the "friendly" URL above as a table's primary key, I would (quite correctly) get chewed out.</li>
  </ul>
  
  <p>I said earlier "up to a point" because obviously, URLs can get out of hand.  Here is an actual URL from Amazon.com that I don't think anyone in their right mind would consider "friendly":</p>
  
  <blockquote>
    <p><a href="http://www.amazon.com/Bissell-Kitchen-Housewares/b/ref=amb_link_5001972_17?ie=UTF8&amp;node=694500&amp;pf_rd_m=ATVPDKIKX0DER&amp;pf_rd_s=gp-center-5&amp;pf_rd_r=1ZXNJFE0CCFFDH4B9HGH&amp;pf_rd_t=101&amp;pf_rd_p=405478901&amp;pf_rd_i=510080" rel="noreferrer">http://www.amazon.com/Bissell-Kitchen-Housewares/b/ref=amb_link_5001972_17?ie=UTF8&amp;node=694500&amp;pf_rd_m=ATVPDKIKX0DER&amp;pf_rd_s=gp-center-5&amp;pf_rd_r=1ZXNJFE0CCFFDH4B9HGH&amp;pf_rd_t=101&amp;pf_rd_p=405478901&amp;pf_rd_i=510080</a></p>
  </blockquote>