When both USE="geoip mongodb", something horrible happens in mongodb_plugin.c. This needs to be reported upstream and perhaps we should make the USE flags block each other for now.
Created attachment 336498 [details, diff] pmacct-0.14.2-geoip-mongodb.patch This looks like the proper fix.
Oh look, a contributor. :)
This appears to have been fixed in 0.14.3. Thanks everyone!