AMD64 is an x86_64 architecture and the x86_64 architecture is a multilib architecture. I don't use Red Hat products, but I suspect that Fedora is standards compliant. If Fedora is standards compliant, it has to support both the 32-bit and 64-bit ABI on an AMD64 architecture. Since, you can't build a 64-bit application against a 32-bit library and vice versa, yum is likely installing a minimal set of 32-bit libraries to support 32-bit applications that are or may be installed.
For example, libparted is used by HAL which is used by PAM which is used by Open Office which isn't released by Sun in a 64-bit version. The Fedora guys can reasonably conclude that many people will use Open Office. Thus you need a 32-bit version of parted. Clear as mud, huh?
If you delete the 32-bit versions, they'll probably just come back anyway.
[EDIT:]My Tarot cards tell me you need to add a monitor section to your xorg.conf.