Riding in 8E on a 757 SFO to IAD on Thursday and the passenger behind me had a large bag which she simply put next to me in the spot where 8F would have been, clearly blocking the exit door. 5 hour flight and never was the bag noticed by FAs. And the passenger climbed over the bag 4 times during the flight -- and then over me and the guy in 8D, I guess so she didn't disturb her rowmates in 9!