I use gmail, so I just use the "Report as spam" option. I'm assuming Google uses that information in some way when calculating spam scores. So if enough people do the same, those emails will just start getting sent to spam automatically for huge amounts of people, and therefore punishing those folks for doing it in the first place. That seems more effective to me.

And I just never really had that big of an issue with spam where I needed to black-hole a specific email address. So for me it just wasn't worth the effort.