This seems to happen every year. Virenque used to do this, and Rasmussen did it last year. Someone attacks the first mountain stage as a stepping stone to the KOTM jersey. Sometimes they also end up in yellow. Virenque did it in 2003 after winning Stage 7. Armstrong let him go because he knew he would make up the time on Virenque later.
In 2003, after Stage 6, US Postal Rider Victor Hugo Pena was in yellow, Lance was 0:01 behind. This was a little quirk due to the fact that Pena finished ahead of Lance in the prologue by that amount, and US Postal winning the Team Time Trial that year put Pena into the jersey instead of Lance. Virenque was 1:52 behind and 1:51 behind Armstrong.
On Stage 7, Virenque attacked solo. He was first over Mont des Princes, Cruseilles, La Ramaz, and Les Gêts, and put 4:06 into Armstrong and taking the yellow jersey and the polka dots. He found himself with a 2:37 lead over Armstrong.
Stage 8 went up l'Alpe D'Huez and while Iban Mayo was the one to win this day, Lance was in yellow by the end of the stage. Lance finished 3rd, 2:12 behind Mayo, but 7:17 ahead of Virenque. After his breakaway the previous day, the polka dot king was gassed going up France's most famous mountain.
So I guess what I'm saying is that while Dessel and Mercado had perfect days today, I'm guessing they will pay for their efforts over the climbs tomorrow. Tomorrow will be a battle between Landis, Hincapie, and the T-Mobile guys. Don't be shocked if the winner of that battle tomorrow ends up in yellow.