Looks like aptitude doesn’t install the start commands. So to make sure it starts properly when powering up you need to do this:
ln -s /etc/init.d/snmpd /etc/rc0.d/k84snmpd
ln -s /etc/init.d/snmpd /etc/rc6.d/k84snmpd
ln -s /etc/init.d/snmpd /etc/rc2.d/s16snmpd
ln -s /etc/init.d/snmpd /etc/rc3.d/s16snmpd
ln -s /etc/init.d/snmpd /etc/rc4.d/s16snmpd