And it's an embarrassment when it happens.

I remember a football game where fans threw bottles at the refs (it was after a utah game I think), and it made me upset with the people who would do that (being a sports offical myself).

I think those incidents are why BYU puts the nets up.

I don't know exactly where the bottle came from... but usually those nets are pretty wide.

Anyway the point is that BYU takes reasonable measures to ensure safety, and utah doesn't.