I really don't get this... Maybe I'm just not clever enough, but this is referring to verification of the email address, right? I wonder how many users don't e

I really don't get this... Maybe I'm just not clever enough, but this is referring to verification of the email address, right? I wonder how many users don't ever verify their email address though... Couldn't facebook instead just make you verify it? i.e. not allow / limit use of service until you've verified your email address?