Yes it is. Because the Uno (or compatible) had limited digital inputs, and they were using one of them up for each of the buttons, that limited the number of arcade buttons that design could use.
If you already have a mega ( http://arduino.cc/en/Main/ArduinoBoardMega
), it has 54 digital IO pins, which means you could extend this simple design out to 54 arcade buttons !
Alternatively, if you've not bought your Mega yet, and you have a Uno or compatible, there are ways to address more than the standard number of pins by adding digital inputs using shift registers. Here's a page for adding 8 switches using a shift register IC http://www.arduino.cc/en/Tutorial/ShiftIn
(note you cascade a 2nd to get you 16 buttons like you're wanting, only using 3 digital pins so you're left with even more to play with if you want).