Comparing the physical feats of the TdF to the popular sports is silly. Not even close. What these riders do is nearly unhuman.
The downside of this, IMHO, is why cycling is THE testground for all performance enhancing drugs. I do not mean this as a cheap shot.
No other sport will test the effectiveness of increased power, stamina, and recovery like cycling will.
I think you have a stream of people willing to risk getting caught (as this is all a cat and mouse game)
Plus they are tested so much - the makers of the drugs find out clearly what can be caught with the current testing technology.

I am so pumped either way - this is my first year to watch the TdF as a cyclist and a fan. I will log a lot of hours on the couch and the lemond revmaster watching versus!!!