Didn't see this before I posted. You got it.
The chunk of foam appears to jump into a 500+ MPH (Delta V)airstream and, for the most part, remain one piece. That appears to be some pretty tough foam insulation. Only after the strike with the orbiter wing does the chunk turn to dust. There had to be some serious kinetic energy stored in that chunk of foam.
Imagine swinging a baseball bat made out of the stuff, as hard as you can. The speed at the tip of the bat is going to be in the neighborhood of 80-120 MPH, depending on the strength of your arm. Now imagine whacking a piece of Grandma's china during the swing . . .
Now imagine swinging the bat at least four times faster and smacking a tile known to crack from the impact of a quarter dropped from two feet.
Knowing how fragile the tiles are, I am puzzled by NASA's spokespersons wanting to take that event off the table . . .