No it can't because no personally identifying information is sent to Apple. Registation of iLife does not allow Apple to identify the exact copy of iLife that was installed, nor does it allow them to identify your computer or you directly.
I registered iLife '05 when I first installed it. If I took the same DVD that I used to install it and installed in on a different machine, then registered it again from over there (with different information), there is no way that Apple could tell that I had used my license illegally nor identify that that particular copy of iLife '05 was installed on more than one machine.
"Registering" with Apple simply means telling Apple that you use iLife software so that they can send you emails about iLife-related stuff. It does not permit them nor even enable them to detect or track illegal use of the software.