Luckily I managed to block much of the spam I got before, so I don't see the current spam behavior. But some years ago, there well existed some non-viagra style spammers that just put dubious unsubscribe links inside. I never tried myself, but was warned that they use the information against you. I would guess, that verified eMails have a greater value ... but it also might be negligible now, since with bot-networks spammers don't need to care if they send 1 billion or 10 billion eMails ...
