This Microsoft patent for acoustic caller ID seems ingenious. Instead of relying on the phone company to ID by easily spoofed phone numbers, the system IDs by voice. That way, callers can be identified from whatever line they call from, cell, voip, landline, and gas station pay phone. Of course, that means the caller has to actually talk before the person picks up the phone.

So smart, yet so dumb.
Patent 7,231,019: Automatic identification of telephone callers based on voice characteristics [USPTO via Wired]