I found a similar sketch to test the i2c bus for an arduino.

Code:
/ This sketch tests the standard 7-bit addresses
// Devices with higher bit address might not be seen properly.
When polled it reported one device found at 0x21

I have no idea why when I do the same with the PBP code it reports 128 devices found at all the even addresss (0,2,4,6,8,0A,0C etc etc)