I have been pregnant 5 times, and I have never had implantation bleeding.
It is very rare, in fact. For every thousand letters on here hopefully asking if some bleeding could be implantation bleeding, we might hear from one person who says she really had implantation bleeding.
Some women don't even notice, or bleed...I never had any form of implantation bleeding for any of my three kids...but then some women do have bleeding...Everyone women is different...