Before I post my thoughts I'll set out my position. I don't have any formal study of exercise physiology, I've read a number of books on the subject, so am no expert just interested in the topic of this thread
I know this is completely unscientific, I watched some of the Vuelta last year on one of the mountain stages Contador and I think Rodriguez rode away from the leading group in very much the same way as Contador and the chicken did in 2007, there was no response what so ever and they both looked like they were sat on the back on a Sunday ride to Mrs Miggins Pie shop somewhere in the Cotswolds. It seemed to me at the time that none of the other riders were able to up the pace to go with them, it wasn't a super aggressive attack, the pace went up and off they went. I can't remember which stage it was but I just remember thinking at the time, wow thats interesting......
My immediate reaction was they must be on something, it just didn't seem believable.
I would be very interested to hear the thoughts of others who have much more knowledge than I do about the power data from the vuelta last year and see how that stacked up compared to the TDF last year and whether the performances were suspect or not