[X-Unix] Why does mDNSResponder have User ID = 4294967294?

[Jerry Krinock]

I did a "ps -alx" and found the following process.  I've seen this guy
before.  

UID = 4294967294
PID = 190
PPID = 2
CPU = 0  
PRI = 31
NI = 0
VSZ = 27996
RSS = 780
WCHAN = -
STAT = Ss
TT = ??
TIME = 0:04.88
COMMAND = /usr/sbin/mDNSResponder

According to Apple developer docs, this "Multicast DNS Responder" is there
for Rendezvous and "is built into Mac  OS X 10.3.x. mDNSResponder listens
for and responds to DNS-formatted query packets sent via  IP  Multicast  to
UDP port 5353".  So it looks legitimate, but why such a strange user ID?
The system is usually UID=0.