jdMorgan - 11:18 pm on Mar 14, 2010 (gmt 0)
The number one problem we see over in the Apache forum is the use of a URL-to-URL redirect when an internal URL-to-filepath rewrite could be used. This latter method is implicit in Tedster's comment about "migrating within a site, for example if you change your CMS. Now there's a case where I prefer not to use a 301, but to retain the old URLs if at all possible."
It is important to remember that URLs and filepaths are not at all the same thing, that they are associated but not equivalent "addressing methods," and that this association is a function of the server itself. Because of this, you could re-arrange and rename every single directory and file on your server, but retain the old URLs (even if this is an extreme hypothetical case). Nevertheless, we see dozens of Webmasters posting that they've changed their server file structure and therefore need to (301) redirect all the old URLs, when this is not in fact the case: All that is required is to internally rewrite the old URLs to the new filepaths.
It is interesting that Google de-values redirected URLs. Hopefully, this is not true (or the devaluation is only slight) when the purpose of the redirect is to cure a problem for which no other solution is available.