Every now and then I like to write about a basic SEO thread and here is one named How Google read ULR with "#" at WebmasterWorld.
The member asks this question because of all the duplicate content issues people have these days.
There are about two ways to have URLs with the # (anchors) in them, that I can think of right now.
The basic method is deployed here on some individual archive entries. Kim Krause posted an entry here the other day at https://www.seroundtable.com/archives/003204.html but you can also get to this entry by going to https://www.seroundtable.com/archives/003204.html#more. The latter URL anchors you down to a place in the source code that looks like
Same page, same source code, and same URL as above. It is fairly easy for a search engine to assume that they can strip off the # and anything after the # from the URL.
The second type of URL is found a lot in dynamically driven sites, including many forums. I often link directly to a post that way. For example, in my coverage of Expanded Broad Match Hurting AdWords Advertisers I link to a thread at http://forums.searchenginewatch.com/showthread.php?t=9817 but I also link within that thread directly to a members post at http://forums.searchenginewatch.com/showthread.php?p=72232#post72232. Two URLs, same content on the page, same source code, duplicate content. Stripping off the # and whatever is after the # doesn't help with the duplicate content issue. I assume built into these forums are methods to tell the search engines not to index that URL but the primary thread URL, but I didn't look.
Forum discussion at WebmasterWorld.