Nmap compiled on Ubuntu 14.04 with the shared instance of libpcap is reporting lost packets, which in turn significantly impacts performance and quality of results. However, simultaneously running Wireshark on the same host does see them. The same issue is not experienced when compiled with the included instance of libpcap.

Details are available at http://seclists.org/nmap-dev/2014/q2/538

Possibly related:
http://seclists.org/nmap-dev/2014/q2/548
http://seclists.org/nmap-dev/2014/q2/341