This is a FoafVocab issue, documented as such by linking it from the IssueTracker page.
Current status: open, with proposed resolution at NamesInFoaf (pointers there to where intially raised, discussions etc.)
Summary: ...it turns out that the concepts of "first name", "last name" and even "family name" apply to only a small subset of the worlds population, and even within cultures with those notions there are exceptions to the rules, e.g. the Danish royal family that only has first names. (NamesInFoaf)
Proposed solution: Let's keep foaf:name, dump the rest of the existing name-related properties, and create a new set of classes for sortable and searchable personal names, suitable for world-wide deployment. [in a new namespace?]
see also Morbus's email to rdfweb-dev
I've outlined another way to approach this issue in NamesInFoafAlternate -- IanDavis
When an issue is resolved or its status w.r.t. the FOAF spec changes, that changed state of affairs should be documented somewhere less transient than the wiki. See IssueTracker for more notes on issue management conventions.