One of my current projects, named Concordia, aims to bootstrap a graph of open, linked data for ancient world studies. Our decision to defer use of properties of the CIDOC Conceptual Reference Model (CRM) is explained in this memo.
In a nutshell: there's no existing web of CRM-linked data, and implementing the standard gives Concordia no near-term wins. Furthermore, mismatches between the CRM and currently published data mandate a level of effort and expense that cannot be borne at this time. Because the Web is an "open world", CRM details can be added in future, as needed.
Update (2008-12-13): I've received some good feedback concerning non-technical issues that keep museum data shut in and will try to write more about that next week.