I hate telemarketers and SPAM shit over the phone and E-mail with a PASSION! And I do many, many things to combat both. For the landline I do use the aforementioned Nomorobo. I also have the phone line connected to a Dial-up caller-ID capable modem that's connected to a netbook which uses PhoneTray. So if something gets past Nomorobo PhoneTray should grab it. Plus PhoneTray is great with unique rings for callers in my contact list.
Nomorobo is making an App and I told them several times to do it and I bugged the hell out of Cricket to implement it, but the Nomorobo App is going to cost $5/month which is bullshit. I'm not paying anything over a buck a month. If they sold the App for $30 -- I'd take it!
For E-mail I control what E-mail address does what. One for banking, ebay, Amazon, etc. That one doesn't get spam hardly at all and when I ever do get spam I report it immediately to spam cop. I also used and addon in Thunderbird called Abusix spam reporter, but they don't have that service anymore. But I do have my website's MX record report to their server since I use a third part E-mail and not my website host's. I do that to keep people from knowing my true IP behind CloudFlare.
Yeah, the DNT list is a joke in a ½. Been on that thing since 2003 and I still get robocallers, etc. But I do have an account with the FCC and report each and every one. I read that in some cases you could be rewarded a cash payment. Perhaps that's if the robocaller gets sued or something.
Yeah... this shit I will not put!