Fraser

To me it boils down to two factors that should be met:
1) Equivalent or better seat
2) The attitude of the requestees

A few weeks ago I flew LHR-JFK and was in 64K. I had boarded at the beginning of Group 1 and was behind a husband and wife. The husband was held up in secondary security and so the wife went upstairs first. The cabin crew greet her and she mutters back with quite an attitude that "my husband is whatever status and we're not sitting together so you must help us move people so that we can". The crew seemed fairly OK with helping her but it was clear she was in row 64 so I was thinking my prime 64K was going to be asked away. My usual boarding routine is to settle in quickly and get changed into more comfortable clothing anyways. I heard the crew mention "it looks like he is settling in already" so I guess they purposefully didn't ask me. But the guy who I assume was in 64B was asked by husband and wife if he would swap and he seemed OK with doing so. The husband of the duo was Gold (coincidentally followed them into check-in and they sat by me in the lounge) so I'm guessing they were upgraded or booked very late and figured picking random upper deck seats was better the main deck. I had only booked my ticket two weeks beforehand and the upper deck was pretty wide open then. Given their general attitude (from seeing them at close quarters at check-in, lounge, boarding and how the wife barked at me for being too close to her on the upper deck stairs) I wouldn't have swapped just on principle that they seemed demanding, entitled and arsey about it.

I've asked someone twice if they wanted to switch.
First was on an AA ORD-DFW flight in F. The wife and I were on an AONEx ticket and for some reason the day before the flight it dropped from our itinerary. Luckily we got the last two F seats but they were bulkhead windows on opposite sides of the cabin (MD80). At boarding some unaccompanied minor that was about 7yrs old boarded and sat next to me in the aisle seat. I asked if he wanted a window seat my wife was happy to switch with him but it was completely up to him. He seemed more than happy to do so but then I felt terrible because his seatmate arrived shortly thereafter and was about 400lbs. He looked penned in, even in a bulkhead in F!
Second was in Club World on LHR-JFK. Was in 62A with the wife in 62B and there was some issue with her seat that meant it didn't recline at all. When my wife brought this to the attention of the cabin crew they automatically asked the guy in 61K (who had the adjacent seat free) if he wanted 62K instead (noting it was a better seat) and he was happy to do so. We moved over to 61J and K.