When calls go out from a call center (a room filled with 20 - 30 poor schumucks making call after call after call for minimum wage) the automatic dialing system dials 3 or 4 different numbers at the same time. The first one at the other end of the line to pick up the call gets to hear the message and the other 3 calls are dropped. As long as the computer sees your number it will continue to attempt to connect. Once the operator has spoken with you, your number is moved from the active list, packaged with hundreds or thousands of other numbers and sold to the highest bidder.
It may be a call coming from a non-profit organization or political office able to sidestep the Do Not Call List, but by any other name, it's still a telemarketing call. The law needs to be changed to stop all such calls.
What say somebody come up with a call back device that has a recorded msg (your choice of a number of annoying messages scripted to target the telemarketing industry, political offices, and non-profits). When you get these types of calls, you simply program in their number and let the device run for a week or so. Set up your phone to not send out your number, so that on the other end they only see the words "PrivateCaller." Inundate their phone system with these calls. Overload their operation with a time wasting activity - somebody or something needs to answer the call. Fight back!