If I've got 2 (or more) URLs (where the only difference is the hash value) to my homepage will Google divide my page rank between those pages or is it 'safe' to have lots of different hashes in the URL and still keep one page rank?
Example:
http://example.com/
http://example.com/#hash
I would imagine it would help but in a trivial way. It would just add more value to your urls and give your pages some semantic meanings if done properly, which I feel really helps SEO. I don't think Google will separate your rank because of these. We just don't know what google uses for all of its pagerank.
There are, of course, no hard and fast rules for what will help or hurt, because each search engine can rank things however it sees fit. Your best bets are to look at the engines you're most concerned with, and to target them specifically. There is plenty of information on how to do this.
I would hazard an educated guess (but still a guess) that Google is smart enough that they won't "divide" your relevance up among all of the hashed anchors you have.
I would also surmise that it could well help, because search engines tend to look fondly upon urls that point to their content with meaningful, readable words.
I suspect Google ignores hashes entirely, as they are meaningless in a search indexing context.
I would expect that Google is clever enough to ignore bookmarks (bits after the #).
It might be worth reading up on Specifying canonical URLs as well, as this allows you to specify a preferred version of a URL where the URI and/or query string vary.
The way that I see it, is that you've shown 2 URLs, that both point to the same page.
Now, considering that Google searches for pages containing the given search criteria, the bookmark part of the URL would seem to be irrelevant to search results. This leads me to suspect that the ranking would not be 'split between the pages', because there is only one page.
To summarise, I'd concur with ceejayoz.
Just curious ... are these actually named anchors on the page, or are you using the hash syntax to provide virtual "page" URLs to a Flash application?
Also note that the server doesn't receive the hash value in any browser I use. The browser submits to the server the URL WITHOUT the hash character or anything following. After the content comes back, the browser locally interprets the hash to mean look for the anchor having the particular name, and scroll forward in the page to that anchor. Such local processing (scroll forward in page during rendering) doesn't even make sense for the server to know about.
I would think that it is in google's best interest to look at url hashes. Why? Because they have become common place for deeplinking into AJAX features (sub-tabs etc) and flash features alike. Google wants to provide the most competitive search features around, and accuracy is a big feature. If they send you to a page that uses hashes as a deeplinking trigger for tabbed content (by matching ID's to url hashes, for example) and one hash on that page reveals content that is more relevant to your search, they have failed if they do not use the appropriate hash.
I build a lot of tabbed pages like this:
<div id="topics">
<ul class="topic-navigation">
<li><a href="#mullet-hairstyles">mullet hairstyles</a></li>
<li><a href="#bouffant-hairstyles">bouffant hairstyles</a></li>
<li><a href="#flattop-hairstyles">flat-top hairstyles</a></li>
</ul>
<ul class="topic-contents">
<li id="mullets-hairstyles">mullet hair, bla, bla, bla.</li>
<li id="bouffants-hairstyles">bouffant hair, bla, bla, bla.</li>
<li id="flattop-hairstyles">flat-top hairs, bla, bla, bla.</li>
</ul>
</div>
If a user was searching for "hairstyles, bouffants" and the #bouffants hash was not included in the URL, users would land on the #mullets content by default, despite the fact that they were looking for the very different bouffant hairstyles.
Google wants to serve their customers the best possible search results, and I'd be very surprised if they were not aware of this kind of internal linking strategy, so I suspect they pay attention to hashes. The extent to which they pay attention probably depends upon how appropriately named your hashes are etc ...