i spent some time looking through the startup objects and found one gotcha, so i thought i would share the steps i followed to get this all working.
1. open /etc/hostconfig with your favourite text editor and change SNMPSERVER=-NO- to SNMPSERVER=-YES-
2. *optional* amend /etc/snmp/snmpd.conf to suite your environment
3. open /System/Library/LaunchDaemons/org.net-snmp.snmpd.plist with your favourite text editor and update "<key>Disabled</key> <true/>" to "<key>Disabled</key> <false/>"
4. lastly launch the snmp daemon (can also reboot at this point to test).
# sudo launchctl load org.net-snmp.snmpd.plist