Unlike calls made to owners of answering machines, all telephone calls made to voicemail subscribers are completed, even if the line called is in use at the time of the call. The surge in sales of answering machines occurred shortly after they were first introduced to the electronics market. Answering machines enable the customer to hear who is calling before the customer decides whether to answer the telephone, a service voice mail does not provide. Once a telephone customer decides to subscribe to voice mail, that customer can cancel the service at any time.
Telephone companies are promoting "voice mail" as an alternative to the answering machine. By recording messages from callers when a subscriber does not have access to his or her telephone, voice mail provides a service similar to that of an answering machine. The companies promoting this service argue that it will soon make answering machines obsolete, since it is much more convenient, more flexible, and less expensive than an answering machine.
Which one of the following, if true, most calls into question the argument made by the companies promoting voice mail?