Re: Circular bar codes
Because you need to move the scan head acros the lines one at a time, as it's read sequentially.
This is very difficult to do because:
a) the circles can't be read by a linear scanner (the only real way to reliably scan sequentially), as each circle represents 2 data points
b) circular codes are very hard to scan "casually" (ie imagine the scanner is held by an drunk 80yr old with the shakes).
c) circular scanners would be damned hard to manufacture, as the scan method would require increasing/decreasing radius sources, rather than a simple left/right linear scanner.