ZeroMQ compiles to well over 600 kilobytes of machine code (just on 32 bit x86).

  $ size /usr/lib/i386-linux-gnu/libzmq.so
     text    data     bss     dec     hex filename
   662134   12952      24  675110   a4d26 /usr/lib/i386-linux-gnu/libzmq.so

Yikes, is there an operating system kernel with virtual memory, USB support, a few filesystems and a TCP/IP stack hiding in there?

It's like 35% of glibc:

  $ size /lib/i386-linux-gnu/libc.so.6 
     text    data     bss     dec     hex filename
  1917549   11624   11112 1940285  1d9b3d /lib/i386-linux-gnu/libc.so.6

Which is itself heavily bloated, trying to provide as much POSIX as it can.