Sorry, but I screen the calls in my office. If there is no caller id available, or it's only a city and state, I do not answer. I've had to get rid of too many cold calls for unwanted and un-needed crap through the years, that I love caller id. The only unidentified calls I will take are local cell phones, because there is no id provided with them and it's generally one of our subs - and they need answers not voice mail.
I answer the phones at my work and we certainly can't not answer a call. Several of our clients show up with some unknown label on the CID and we can't miss their calls. That being said, when I do answer a spam call my usual response is a polite "No, thank you" or a "We're not interested" followed by a hang up.