This time I actually side with Contador. The facts dont add up
Clenbuterol is a drug I know well for certain reasons, it has a long half life - 35 hours. The dose detected in him was SO tiny, assuming he'd taken the smallest possible dose (say 20mcg once - someone using it as a performance enhancer takes 40-140mcg a day for 2 weeks), it would have had to be in his system for quite some time. This would have been picked up in previous tests - especially as I assume he'd be tested daily on the tour.
There have been many stories of meat contaminated with Clenbuterol - it is common in China, and has occurred (albeit not as often) in Europe/US, so he could well have eaten contaminated meat. "But what about his team mates" - they too could have eaten it, but as the doses detected as SO small, they may have metabolised it quicker and therefore not shown up on their tests.
Not often would I stick up for a cyclist, but I think this time there is a genuine case for innocence!