Lance said that yesterday's stage was a lot different circumstance compared to the one that happend to him and Jan both in 2001 & 2003, so it's hard to say if they should have waited.
After looking back at the replays when Andy attacked, Vino and AC chased him down very hard, then Andy's chain drop. Andy was still pedaling and sitting on his bike when AC passed him. I think AC was so focused that it's so hard to notice Andy had a mechanical problem. Then Sammy Sanchez and Denis Menchov caught up with AC and continued the hard pace who are currently third and fourth overall. AC would have to convince the two riders to slow down and wait for Andy. Do you think they would have agreed? What if Sammy and Denis continued to attack and AC waited for Andy, that would take a lot of time from their lead right?
What I saw Andrenaline was pumping, they were close to the summit of the final climb, so little time to make decisions, it's the final week of the tour and there is a lot of things at steak. They are professional cyclist who are paid to win, so naturally their 1st thing in mind is to win.
Don't get me wrong I feel bad for Andy but I also feel bad for Alberto for getting all the heat he certainly made a lot of people hate him.
If Andy had crashed, maybe I think the leaders would have waited for him.
Look at the video replay, Andy was still sitting on his bike and pedalling when AC passed him on the left. If Andy had already gotten down on his bike and fixed his chain before AC passed, then it would be a lot harder to believe that AC didn't notice the mechanical problem.
http://www.steephill.tv/players/eurosport/v1/?title=Andy%20Schleck%20drops%20his%20chain%20at%20a%20key%20moment%20-%20Tour%20de%20France%202010&id=20948447 
