Hash URIs and RDFa documents

Hi,

Imagine an RDFa document describing a person. The foaf:Document URI is <>
and the foaf:Person URI is <#person> because you want to be able to
distinguish between the two; also foaf:Document and foaf:Person are
disjoint.

<>        a foaf:Document .
<#person> a foaf:Person .
<> foaf:primaryTopic <#person> .

If the document is describing an online account, it might have
<>        a sioc:User .
<#person> foaf:account <>.

My concern is about the #person fragment with regard to the HTML document.
If the page is only about one person, there might not be a tag with
id="person" in the page. Is this a problem? Should I have a tag with such
id, or, on the contrary, should I avoid this as to ensure the resource being
described is not confused with the actual HTML tag contained in the page?

cc'ing Dan since this message is related to his point #5 at
http://danbri.org/words/2010/01/14/549

regards,
Stéphane.