Ah, well that makes sense. Though could you not store last position on the client then just sync on connect? Like, if handling so many events was too much a challenge. Or are crashes that big of a deal? At any rate, I guess that allows you some leeway with the writes - a few minutes of unavailability doesn't hugely impact anyone eh? Fun writeup.
Many devices don't offer local storage to Netflix. Also, if your device crashes or your internet drops, there is a good chance that you're going to try and watch on a different device.
It makes for a much better customer experience if we don't have to rely on your device saving the information and calling home appropriately.