This makes no sense for an anti-spam service. They aren't "signing up", they are "opting out" of all future emails from whatever they are using the email for...so this user will probably come back, but if you spam them even once, you've lost them for life. They aren't the same as "signed up" users for a toolbar or installations of software.
This is a pure ad play, in its current form, and has revenues from that source. There might be ways to integrate this with other anti-spam, anti-malware, privacy, whatever, features to build a product suite that is worth more than the sum of its parts, but right now it's an ad-supported model.
This makes no sense for an anti-spam service. They aren't "signing up", they are "opting out" of all future emails from whatever they are using the email for...so this user will probably come back, but if you spam them even once, you've lost them for life. They aren't the same as "signed up" users for a toolbar or installations of software.
This is a pure ad play, in its current form, and has revenues from that source. There might be ways to integrate this with other anti-spam, anti-malware, privacy, whatever, features to build a product suite that is worth more than the sum of its parts, but right now it's an ad-supported model.