Okay, like many of us, it seems like every 757 and 767 I have been on lately has been packed to the gills. So yesterday, after my flight from SJC-PDX was cancelled due to mechanical, I was rerouted directly to LAX from SJC, which was great since LAX was my final destination anyway. (Was originally doing a mini-mileage run since it was the same price, $154; only needed LAX-SJC RT to see a friend in SJC, and instead booked LAX-SEA-PDX-SJC-PDX-LAX). So anyway, after the TA told me that my original flight was cancelled, she gives me a seat in row 2 on the 400, and tells me she has blocked the seat next to me. The plane is only half-full, and I get comfortable in my seat with the empty next to me...newspaper, book, etc in the empty. The FA announces that since the plane is only half-full, people may move around and take other seats, and wouldn't you know it, some lady comes up and decides to take the "blocked seat" next to me. Not wanting to look at her and tell her she could not sit there, I gave her a pained look and said the words, "I have bad gas", squeezed my nostrils with my fingers, and then put an air-sickness bag in front of my mouth. She quickly left and chose another seat. Sorry, but I just had to do that. Some days you just need your space.