Nothing different from what LinkedIn (annoyingly) does, really, or Facebook, or any service that offers to slurp in your contacts from Gmail. But in this case it's one less step between the spammer and the address book; Google is both.
I was taken in at first too—which means it's well-written satire, if it's not true. But either way, the point is this: learning to look things up is not at all the same thing as learning to learn.