By Keith Weir LONDON, Sept 24 (Reuters) - Marketing experts fondly recall Seoul 1988 as the Games when the Olympic movement put behind it political boycotts and started to develop its true commercial potential. However, the sensational Ben Johnson drugs bust in Seoul and subsequent failure to stamp out doping has meant that athletics - the centrepiece of the Games - has been left behind by other sports in the wider battle for sponsor dollars. ... More...