This idea is in my book ok for 3 or 4 switches. Any serious keypad with 6 or more switches should be done in a matrix.

The "novel idea" from the article has interesting issues. You need a different valued resistor for each switch. Can you imagine the headache you give the assembly people if you tried to build a keypad with say like 36 switches. The single wire idea also has issues of working properly of you detect right as a switch is opening or closing and will have difficulty resolving which switch is more than 1 at a time is held down. With two switches the parallel combination of the two resistors could look equivalent to another switch. I suppose that for a small number of keys and careful selection of the resistors it may even be possible to detect every possible combination of multiple key press.

Michael Karas