I got a total of 15 (fifteen) calls during this year's primary season. All recorded messages. In the presidential election they tried to call my mother repeatedly even though she's off the rolls as she is no longer with us.
As it turned out, in my area they do not have access to the voter rolls. They are allowed to sit in the polling place (as poll watchers) and note the names of those voting and they make up their lists that way. Obviously if someone is deleted from the rolls they have no way of knowing it and they'll keep trying to reach the person even if they're gone or have moved.
Some years ago a large corporation was upset about leaks to journalists and demanded and received from the Bell in the HQ toll records to search for whoever was calling the journalists. Both the company and Bell got into trouble and bad publicity for that antic. I can't help but wonder with deregulation and hungry non-regulated carriers that that sort of thing still goes on under some loophole.
As to the NSA research, frankly at this point I don't have an opinion because there are good arguments on both sides.