I stand corrected, you are right in that it is not mandatory to fill in new details of flights/accomodation etc but one thing I would say is that no one has a right to enter the USA, its under the discretion of the POE immigration officer and I think we have all heard horror stories of passengers being taken into the little room !!! for questioning if they fill something isnt right, I have first hand experience of this when freinds of ours left off the number of our villa when visiting us a few years back. I would recommend anyone taking a few minutes to update their ESTA form each time they fly over.

Luckily we have a B2 visa's so we dont have to worry about ESTA.