Knot, I've wondered that myself. It's been discussed a few times in Versus coverage. From what I've heard, the peloton apparently sits up a bit to "wait" when it's that big a group. I saw a mention in either Stage 3 or 4 coverage, too, that the commentators were surprised that the two riders in the breakaway had stopped for a "nature call", apparently that's an unusual thing.

There are just so many interesting aspects to watching the Tour, aren't there?