I've seen this a lot recently. On a LH flight the other day (row 2, poor seats but the legroom was something to write home about...) the FA was very bothered by the chap in 1D countering that it was normally OK.

I also find the fact that my ipad keyboard seems to be the dividing line between danger and safety slightly bizarre. Admittedly it's magnetic adhesion to the device is not Apple's finest achievement, but it does make me smile when I am solemnly told that it must fold back the keyboard to comply with safety.