A while ago on the ZBB and on the conlang list we had a discussion about 
person marking on nouns, since I'd incorporated it into my conlang at 
the time (which I'm doing a bit of work on at the moment). At the time I 
had difficulty citing a clear example of a natlang that had such 
marking. But, now I have "The Papuan Languages of New Guinea" (Christmas 
Present) I can now reveal that such a natlang is: Alamblak, Sepik Hill 

1sing: -a
2sing: ų
3m: -r
3f: -t

1dual: -nė
2dual: -fin
3dual: -f

1pl: -nėm
2pl: kė(m)
3pl: -m

These seem to be clitics which attach to the end of the complete NP. Eg: 
yima-m "people" vs yima-nėm "we people". I suspect, looking at the 
singular gender distinctions in the 3rd person, that as in my conlang 
this system evolved primarily to classify 3rd person referents for 
gender and number to help distinguish what the verb was agreeing with 
(since the language also has verbal agreement)... the markers used were 
3rd person pronouns, and this usage naturally extended to the use of the 
other pronouns as a consequence. This is only a guess though...