When emerging sys-apps/pcmcia-cs, emerge also did X too. I was going to install X anyway, but this might be more annoying for someone else.
OK, I took a look at this, and if "X" isn't defined in USE then this won't happen. Also, soon we will have some new USE var-related features that will make this much less of a pain. I'm marking this as "WORKSFORME", since the situation is workable now and will get nicer in the future.