Pelican said:... What if the restaurant I ate at used some sort of organic herb in the sauce that will test positive...
Wow, I need to make reservations for that resto! As Carsten says above though, it is indeed a question of thresholds and for everything else, if you want to be a pro sportsperson in today's synthetic world, them's the breaks. I don't think it would be incredibly hard to keep most substances out of one's diet. Otherwise we'd be hearing about a lot more cases than Contador, a ping-pong meatwrong and a cokeynosed kiss.