This ebuild has a DEPEND on ucd-snmp. When the newest version of ucd-snmp is installed, net-snmp-*, "emerge -upD world" complains about missing ucd-snmp. But ucd-snmp is defined as a blocker to net-snmp and vice versa. I modified the DEPEND to "virtual/snmp" and everything works fine, so I recommend this.
the 0.8.x already had this changed so i fixed up 0.6.x as well, thanks