I keep my wallet and passport on my person when flying; for longer flights where I'm likely to sleep, I have a couple of fleece vests with zipper pockets which can hold them much more comfortably (and less likely to fall out) than regular pants pockets.

Neither my computer nor if I'm bring a full-size camera, any full size camera, are going to be easy to bring out of my bag discreetly. On a short-haul flight, I'm not going to miss someone taking my whole giant backpack regardless of which side it's in; on long-haul where I sleep, which side it is won't help avoid it being taken while I sleep.