Never heard of this happening before, but maybe it's more common than I thought.
My GF flew from BOS-LAX today, and across the aisle was a mother w/ her toddler. The toddler was watching a Sesame Street style DVD, but was not using headphones. Thus, the ABC Song and Sheryl Crow's "Soak Up the Sun" played ad nauseum for the six-hour flight for the enjoyment of that area of the cabin.

Two questions.
1. Do people actually do this, or is this a freak occurrence?
2. Is there some sort of valid reason for it (e.g. toddler can't wear headphones), or is it just rude?