It's definitely better if you eject it before pulling the cable but it most likely won't screw anything up if it's just sitting there charging. I've pulled mine out without ejecting a few times and no harm done.
Right, I don't think ejecting does anything technical (like ejecting a USB drive does) but rather it's for the USER's benefit to make sure they look and see that iTunes isn't actually syncing anything at that moment. If you know that iTunes isn't currently syncing, there's no problem with just unplugging the phone.
It's definitely better if you eject it before pulling the cable but it most likely won't screw anything up if it's just sitting there charging. I've pulled mine out without ejecting a few times and no harm done.
That makes it sound like it isn't even harmful to anything to unplug it when it is the middle of syncing; the only thing bad is that is just won't finish syncing.