Since more and more users are ditching their landlines, what other option does a poor telemarketer have?

I'll put the spam caller (robo or human) on hold and let them spew their message into hold -- the theory being that this will waste a little of their time and dent their productivity a bit. Hopefully, more and more victims will do this and the cold calling scheme will become less attractive. There is a risk, however, because my number might then be flagged for "interest," because I listened to the call, and the number will be dumped into a "recall" list.

Lately, I've been getting calls from "your computer support center". They have noticed that my computer has a problem, is causing trouble on the Internet, and it must be fixed NOW. I am ordered to go to my computer, NOW. (good luck with that) If I have a few minutes or I'm in the mood to be mean to someone, I'll ask them to give me my IP address. They always chafe at this. In many cases I'm not convinced that the person knows what this means, but one guy (I recognize his voice) has been through this before and will spout off an address that is on the wrong subnet. I'm not sure what they are selling. I assume that they want to take control of the computer, scan it, and they'll discover some "threat" that must be fixed for a fee or they'll simply deliver a malware payload.