Personally, I think telemarketing companies are lower than pond scum.  If I need your product/service I will call you.  Do not call me during dinner, my favourite TV show, my quiet time with my family to attempt to interest me in things that I am not interested in.  Tar and feathering is too good for these people.

My cell phone is actually my company-issued cell phone which has caller ID and call answer.  Even now, if I don't recognize the phone number, I don't answer.  If it is important, they'll leave a message, if it is a telemarketer, they won't.