100% Click Through Rate

It's very important for startups (and everybody else, for that matter) to learn from Facebook here. Straight to the point and I don't get the spammy(?) feeling I get from a lot of the other services I use. Great emails. (And I actually think I also have a 100% CTR on email from Facebook.)

Makes sense to me, in light of the difficulty of navigating to many pages on Facebook. Links are about the only way to get around quickly.

Am I the only one who absolutely hates Facebook's email notifications? I turned them all off because I just don't care when someone tags me in a pic: to me that's just more spam.

How would you measure the click through rate of facebook notifications? Also, why is the click-through rate of notification e-mails important?