http://www.mydomainname.com/blog/blog/29/blog/blog/blog/blog
/blog/blog/blog
/blog/blog/blog/blog/blog/blog/blog/blog/blog/blog/blog/blog
/blog/blog/blog/
blog/blog/blog/blog/blog/blog/blog/blog/blog/blog/blog/blog/
blog/blog/blog/b
log/blog/blog/blog/blog/blog/blog/blog/blog/blog/blog/bl
I'm pretty sure it's related to crawlers not respecting the baseurl tag.
Ah! That would explain why I see the same behavior with my Atom feed - the offending party is ALWAYS Google Desktop.
-- Adam