There is an interesting Google Webmaster Help thread of an example of what is called a cyclic redirect. Basically, when you point URL A to URL B and have URL B point back to URL A. It is a cyclic nature and can cause issues for Google and other search engines.
The webmaster came in asking "why is GoogleBot reporting a "Redirect error" on all pages it crawls? promptly saying: not indexed."
The issue was he had both http://www.max.grenkowitz.net/ and http://max.grenkowitz.net/ resolve to the same page. As JohnMu of Google explained:
A) http://www.max.grenkowitz.net/?topic=10 .. contains link rel="canonical" href="http://max.grenkowitz.net/?topic=10"/B) http://max.grenkowitz.net/?topic=10 ... redirects back to A)
For our systems, this looks like a cyclic redirect, making it hard for us to follow and pick the right URL to actually index.
One way to resolve that could be to use the final URL as the preferred canonical one.
The webmaster fixed it, as far as I can tell from his source code, so Google should pick up on the change soon.
But sending Googlebot in circles might not be a great idea.
Forum discussion at Google Webmaster Help.
