Scammers know when an answering machine will pick up and always seem to end the call just before that happens. Do not call list is a expensive joke on the taxpayer that either does not work or is not enforced hard enough.
The DNC costs taxpayers nothing since it is funded by the subscriptions fees paid by legitimate telemarketers. But then i am sure you blame every law whenever a criminal breaks it right? After all it isn't the criminal's fault, it is the fact that someone stupidly made a law preventing something from being done.