Specifically, Leopard's tar command. Now it, when you are creating good old .tar.gz archive, will also try to slip into it a bunch of files with names like ._.foo.xml, if your archive to contain foo.xml file.
Wisdom of internets (Leopard's tar is broken, OSX considered harmful) pointed to the solution:
export COPYFILE_DISABLE=yIt's going straight into my
~/.profile.