This summer at WDW my family and I were at Rainforest Cafe chatting about our day while we waited for our food to arrive, and I happened to look over at the table next to us - the dad was playing on his phone, the two little kids were playing on ipads and one kid was playing his nintendo DS, and the mom looked bored out of her mind. I remember thinking it was such a shame they were missing out on a chance to enjoy each others company and the experience of the theme restaurant.
Maybe they had had enough of each other's company and this was the best option for them to not kill each other?
I would not bring my iPad into the parks. Mine stayed locked in the safe during the day. It doesn't take that great of pictures and is very distracting to other guests.
And I think people just look silly using them to videotape and take pics. They're so big!