I specified -recursor 8.8.8.8 thinking that should just work. It launched successfully then only showed this error much later:

    2014/02/22 09:09:06 [ERR] dns: recurse failed: dial udp: missing port in address 8.8.8.8

We should probably just default to port 53 if no port is specified since any recursing DNS server will likely be on this port anyways.