RL/SD, I believe it was the 4th or 5th stage last year as well, that Armstrong took the lead, almost by default, and then surrendered it a few days later, only to demolish the competition once they hit the Alps.
I think this may be the same strategy once again
EDIT - It was the 5th stage last year.
Here's a good breakdown on this ESPN.com story about where Lance was at in relation to leading/being behind from 1999 up to the 5th stage last year. Looks like it varies from year to year.