I agree with this article, I definitely get less telemarketing calls since I signed up for Do Not Call. I signed up for the New York list when it first came out. That was quite a while ago, and although it took a little while, it was effective. I guess now it has been converted to a Federal registry, I know it was automatic if you were already signed up at the State level.
In terms of spam, I am not sure. I still get too many, but I think the number may have decreased. Whether that is because of the registry, or spam blocking features in email, who knows?
I should sign up for paper junk mail elimination too, although I think that is still cumbersome, not an easy website process like Do Not Call. Hmmm. Something to investigate. Every two weeks we have curbside pickup of paper for recycling, and I can never believe how much of the bin is junk mail, especially annoying credit card offers. Such waste!