when i went into the apple store and held the ipad 2 the contacts where set up by email.. but every one i have facetimed with on my iphone i have their number as well so i dont know.. i assume on the ipad its done by email .. maybe some one can confirm
well on the ip4 you get a facetime button on the contact so you sont have to ring them first then use facetime just facetime straight away, maybe that uses the email
this is the answer to mu question. No, its seems that iphone4 is not capable of Facetime via email. It needs to have a contact number, there fore it needs a service.