The FAA requires us, at Alaska, to do an exit row briefing on every flight and recieve a verbal confirmation from each person in the exit row that they heard the briefing and are willing to perform the functions on the card. Not everyone does it, like they're supposed to, just like not everyone enforces the carry on baggage rules in row 1 and row 6, though I think that you'll find more F/A's doing the exit row checks than not.

Each airline has a different cabin safety inspector from the FAA and each cabin safety inspector interprets rules differently. This is why you might see Southwest F/A's moving around during taxi, taking beverage orders, and that's okay with their FAA inspector. Our inspector interprets the rules to mean that we are not permitted out of our seats during taxi phases of flight unless it is to perform a safety related function.

Maybe that helps to explain at least the exit row part of things. I also require that each person in the exit row listen to me and verbally acknowledge that they heard me. Besides it being my job, I also think it's rude when it's very evident I'm talking to them and they try to ignore me by continuing to read their book or magazine. I don't go into a whole speech about the exit row, I just ask each person if they are willing and able to perform the functions listed on the card. I usually say it once then look at each of them for an affirmitive answer.