bloupbloup - 7:34 am on Jul 19, 2012 (gmt 0)
I see that most of the people here know their subject.
In my experience:
1. First of all, I have witnessed that xml sitemaps are indexed in google and appear in search results. You can witness it by typing: "site:*/sitemap.xml" in google. Today, we have not one sitemap but several several sitemaps (post,page,image,news). So, it is more garbage for our results. Knowing they don't have added value from content point of view, i wonder what is the impact for our indexing. Let's remind you that when googlebot indexes files, it values content. However there is no content in xml sitemaps but only links. I wonder if google considers it as a regular xml file in the context of pagerank. If it is the case, it is really bad, because xml sitemaps are going to have a negative impact since there is no real content in it.
2. I installed the module called phpbb seo to my phpbb forum. At the beginning, i installed this module that add a URL with the topic name in it rather than "viewforum.php"
So i had two URL for each page. "viewforum.php" version of the URL and "/my-topic-forum-name/". I also had a sitemap listing the URLS with topic names. I wanted to have the topic names URLs to be index and NOT the viewforum.php?f=#*$!
However google indexed both. It did not take account of the URLs in the XML sitemap.
Btw, i solved this issue with another module that did 301 redirect from viewforum to the topic name. So xml sitemap does not indicate which URLs to index.