Imprinting is an interesting concept.
It's a legitimate animal behaviour, which I find makes for a nice comparison. I.e. 'Real Life vs. Twilight.'
Konrad Lorenz first experimented with imprinting using Goslings. He took eggs that hadn't been hatched yet, and made sure that he was the first thing they saw upon leaving the egg. As a result, the goslings imprinted on him, and recognized him as their mother. I could go on about how they would then refuse to mate or interact with their own species, instead attempting to court other humans, and how that could possibly be applied to Jacob, but I digress (as in, will he abandon his own kinds for vampires or half vampire after imprinting on one?).
The thing that I find most interesting, is that Konrad Lorenz discovered that animals only imprint within a "critical period." This is a short period of time when an animal is first born. An animal won't imprint after this period. In Meyer's novel, the wolves can imprint at any time in their lives, even late into their lives. Whether this is intentional or not, it provides an interesting contrast between reality and fiction, and adds another subconscious layer of distinction between what we're reading, and what is commonly accepted.
=] Biology FTW.