I have to admit, that I am also one of this very bad seat stealers for babies. I take my infant on the lap with me, if there is space, I give the free seat to my baby (in a car-seat for babies). It is safer to go by car, on the lap or in a seat.

But good to know, that this is quasi a crime. The next time, if my neighbour leaves his seat and moves to a free row of three-seats in order to sleep, I will call the FA, because he has to pay two additional seats...